Need a photo looking down in the frame with the slide removed to make sure you installed the FCG correctly.

Next, strip the slide, and start checking the FP channel end channel and FP  plunger channel for over spray that may need to be removed in the channels.

Hell, Who knows and you may have melted the liner during baking if you did not remove it before coating/backing, or when the slide was machined with it in place,  and it needs to be replaced.

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FP block plunger should not be locking, it should be able to be pushed up with ease against the light spring tension, the FP should move forward to allow it tip to protrude out the front of the bolt which will hold it forward, and when you pull back on the striker, Plunger should drop back down.

As for FP liner, depending on how you pull it, you pretty much kill it, and it will need a new one. Hence the Fp can not bind in any way when the FP is moving through it, and it has to be fully seated forward of you run into problems as well.  Also, using a seating tool, so you don't destroy the new one.

Now with the FP sleeve out, take a very good look in the channel to make sure you did not get any coating in the channel.  Hence before you bake, you use Acetone on a Q tip to make sure any coating in the channel is removed.  Same goes for the plunger channel as well.
Now with the slide bake, acetone may still work, but it going to take while/work to dissolve any baked coating in the channels.

Hence any coating in the channel is going to end up not only making the ID of the sleeve smaller when seated that will cause binding of the striker to the sleeve, but if you did get coating at the end of inside of channel, going to cause the FP to not fully produce out of the bolt face as well.

Next on the RMR non ejection side bolt to hold it down, you may have to trim that bolts end since it down the ejector spring side of the slide and may be a touch too long.  The easy way to check is to pull the extractor, the spring and rod, and back shine a light down the channel to make sure the end of bolt is not protruding in the channel.  hence if it binding up the rod and spring, this is going to cause problems with the slide locking up as well.

As for the real problem, when you coat a glock slide without removing the old coating, you do not coat any part of the inside of the slide, since it will cause problems with barrel lock up with the coatings too thick.  If you do want to coat the inside of the slide so it color matches the rest of the slide, then the factory coating needs to be removed first, and the new coating inside the slide completed with a thin coat mixed to 12/1, and even a touch of thinner used so it produces as very slick finish inside the slide areas.

So right now, I can tell that you painted the inside of the slide over the factory coating, since the hood of the barrel is not even with the top of slide, the slide it not all the way forward at lock up on the frame,  meaning that the barrel is not fully locked up correctly to the side, and the striker is hitting the FP well above the center of it and not full protrusion since the barrel is not fully locked up the the slide to begin with.



So, since the coating has already cured/baked and not going to come off easy from the inside of the slide with acetone and scrubbing, time to pull the RMR, FP sleeve and sights, bead blast the coatings off the slide to get it down to the bare tenifer metal finish, and when you do coat the inside of the slide now directly to the tennifer metal finish this time around, light coat only at 12/1 mix with thinner for your base coat to start with so the inside of the slide coating is slick semi gloss finish and a very thin even coat.  Also,  clean the FP and plunger channels of any coating with Acetone and Q tips, before baking.

Now with the base coat cured so you  tape off the insides of the slide so your not adding more coats to the barrel contact surfaces inside the slide to cause barrel and slide lock up problems, then you add more coats to the outside of the slide as needed  with a 24/1 mix if you want more of a flat finish to the outside of the slide, remembering to clean both the FP and plunger channels before baking again as well..

Trust me, you still have problem with the front of barrel hood cut  to the bottom side of slide surface with too much coating build up there, since your slide is not moving all the way forward on the frame when the barrel goes to lock up in the slide.

Hence with the added build up on the bottom of the slide just in front of the hood cut area, this is causing problem with the barrel back  lug flat not having enough room to move forward enough on the frame locking block to allow the slide to go all the way forward on the frame.


So again, your slide is short stroking about 1/8" short of where it should be all the way forward on the frame, since the build up on the bottom of the slide is too thick where the front hood cut ledge just in front of the hood contacts the bottom of the slide.

So trigger pin, right above it where the barrel lower angle and flat seats against the top of the frame lock block and if you look at the flat in front of the barrel hood to the bottom of the slide, this is where the coating was build up too much, and why you have the bind of barrel bottom to top of frame block, and why the slide is not moving all the way forward on the frame.


Hence the barrel and slide locked up correctly on the frame (barrel fit to bottom of slide and frame locking block), the back and front of  slide to frame should look like this on the frame.

And why your slide is not in the correct position on the frame for the trigger bar tab to push the FP stop plunger all the way up enough correctly when you pull the trigger to allow the striker to pass by it cleanly.

Again, the barrel flat just in front of the hood, and the coating to the bottom of slide there is too thick, preventing the barrel just in front of the hood to raise up enough to all the lower barrel lug flat/ramp to slip forward on the frame block, to allow the slide to lock up correctly all the way forward on the frame.

So if just the slide was coated and not the barrel, it just this area on the slide for the barrel's top flat just in front of the hood that the added coating needs to thinned down.  
If the barrel was coated as well, then both it's coating on the  top flat in front of the hood  will need to thinned too, as well the flat and ramp area on the barrel's bottom lugs the the coating has build up as well.

Hence barrel  is no able to move up high enough in the slide, for the lower barrel rear lug flat to glide forward on top of the frame locking block flat, for final slide's movement to lock up to frame all the way forward.

Should not need to sand much, and it just the milled flat area in front of the barrel hood that will mate up with the bottom of slide that needs to be thinned down on the inside of the slide; so the barrel can raise up in the slide enough for the lower lug flat to lock into place.



Also, Watch the over all barrel hood to frame slot fit as well, hence they are the tight side to begin with, but may have build up enough on the breach face and back edge of the front of side opening for the hood, that may be causing binding issues as the hood is trying to lift the final way up in the slide cut out for the hood at final lock up as well.

Again with the barrel locked up correctly to the slide and frame locking block, the slide to frame, front and back, should look like this,


And yes on new FP liner, since once you pull the pull the slide back plate, and push up on the FP stop plunger, the FP should free drop out of the slide with the slide muzzle pointed upwards. I have seen the 800 sand paper trick to try to save them, but with the sleeves so cheap, just install them the correct tool, no coating build up in the channel that will reduce its ID when pressed in place, and bob is your uncle for a very long time before they even think about wearing out.