You lost me on using car oil, instead of CLP to clean and lube the rig.

As for quick checks, make sure that the bolt catch assembly threaded end section is flush with the face of the mag release button,

That the bolt catch can move freely in the upper under the light spring return tension (empty mag lock into the upper with the upper shotgun opened will raise the bolt catch all the way up, and not a problem with crap in the bolt catch spring channel or not drilled deep enough to cause too much spring tension that the mag spring tension on the empty follower can not push the catch all the way up),

And when you pull the charging handle all the way back, the front face of the bolt stops about 1/8"~1/4" in front of the back of ejection port window, and that the last half of the charging handle pull does not increase in tension to get the bolt all the way back behind the bolt catch.

Short of this, pull the mags apart to give them a good CLP cleaning, and make sure that the follower skirts don't have over castings that will cause them to drag on the inside of the mag bodies.

Also, when the bolt is locking back, make sure its the bolt catch in front of the bolt face that is locking the bolt back, and not just the catch catching the bottom of the carrier instead.  Hence if rig is correctly full stroking, then spent case should be ejected a good 10'~15' out of the ejection port window, and puts the bolt behind the catch on a empty mag to raise the catch all the way up.

And since I bring up charging handle pull tension for that last inch back, if you are feeling tension, and have the correct length recoil spring in play, may be a problem with the hammer tail being too long, and causing hammer binding between the top of trigger and bottom of carrier.  So make sure to check the disco spring to make sure it installed large coil side down into the trigger slot, and the back of the trigger and disco tails for sighs of denting from the hammer tail as well.

Clipping the bolt catch spring is an option, but I just re-mill the spring/buffer channel to the correct depth since part of assembly is cleaning up the spring/buffer channel since they are often packed with blasting media to start with,  while checking its depth as well.