I have a Glock 21SF with picatinny rail and ambi mag release. I have had some issues with it not wanting to catch the magazine when inserted, and I have a couple questions.
First off, tracking the issue and that Glock will replace the frame. Ideally I would like to find a fix and keep the frame since it is pretty cool and rather rare.
1) Is there an aftermarket ambi mag release that will replace the factory mag release and solve the issues people have been having with the mag release sticking?
2) Would it be worthwhile to buy a stock of factory ambi mag releases and springs and just continue to replace the parts as they start to not function properly?
3) Is there any other info anyone can shed on a fix for the problem?

Thanks in advance.

I am interested in this as well

This must have been common.

I had one of those exact same pistols and it was impossible to drop a loaded magazine without pushing up on the baseplate while hitting the mag release.

I got rid of it and bought a newer 21SF with a Glock rail.

IIRC Glock will replace the frame with std release.

I am tracking they will do this, but I kinda want to keep the current frame. Just trying to see if there are any aftermarket mag releases or any fix that anyone knows about.

I just got a 21SF with ambi mag release and the standard Glock front rail, and I'm having problems with the mag release as well when trying to seat fully loaded mags. Does anybody know if Glock will replace the frame with a standard mag release 21SF or if that's only for the frames that have picatinny rails? 

I think it's the Pic rail. If memory serves, they were issue way back and is why they changed.....

Honestly, it's hard to remember. Call Glock to find out.

I know my 21SF does not have a issue, it was a LE trade.

I would "not" want my frame changed unless I just had too. Matching serial
numbers is one thing I look for when buying a used Glock. Not that it
hurts one or affects it's reliability, I just like matching numbers on used Glocks.

I don't know of any aftermarket fix.  I ended up with a used 21SF with the ambi mag release recently and had the same known issues.  Hard to seat a full mag, hard to eject a full mag.  My release would stick to one side once it did release the mag.

I called Glock a day or two ago and talked with a service tech.  He said to send it to them and they'd swap the frame.  I filled out the service request form from their website and sent it via FedEx this afternoon.  Standard next day was $45 from TN to GA.  I sent the entire pistol.  I expect to get back a gen 3 SF frame with the standard mag release and my same slide which will leave me with mis-matched serial numbers. Others have posted about getting the same serial number with a -1 at the end.  Some have posted that Glock threw in night sights at no charge.  I've also seen posts about some people getting a whole new pistol with matching numbers.  Whatever they send back will be an improvement if the mag release works.  

Anyway, I shipped it about 2 1/2 hours ago and already got a notification that it left FedEx and is expected to be in GA by 3pm tomorrow.  Tech told me on the phone that turn around was around 2 weeks, so I'll post some updates.

I have one of these with the pic rail and the mag release sticks to one side. I'm about 2 hours away from Smyrna...

This may give me a good reason to ride down there and check the place out. Maybe they could swap it out while I wait.

FWIW, when I took the armorer's course they said that it was an inherent issue with the design and that's why it was phased out / they offer the frame swap. If you're dead set on keeping the frame I'd just build up some part stock so when it starts acting wonky you can swap it out. I wish they'd have stuck with the 1913 rails though.

Thanks. Figured this was going to be about the only way to go. Is it the design of the frame or the design of the mag release that is causing the issues?
Also, I am assuming that because of how the frame is cut for the ambi release that an aftermarket mag release cannot be swapped in, correct?

I think it's a little bit of both.  If you look in the mag well and see the lever that moves to release the mag when you push the release, it's above the mag release button.  That's why the magazines that came with this model have the extra indention and why normal 21 mags (without the extra indention) won't seat at all in the 21SF ambi model.  Since the aftermarket release engages/releases the magazine in a different manner, they won't work in the ambi model.  I have a 30s as well and bought some 21 mags to use in both pistols not realizing the extra indention issue at the time and they wouldn't seat in the ambi model 21SF.  If you scour the gun stores you might get lucky and find a factory mag with the extra indention, but so far I've only found one in over a year, so I only have 3 mags that work in the ambi model.

There may be fix out there somewhere, but like Sheepdog said, I think spare parts is about the only way to go without having Glock swap out the frame.  After all the times I couldn't get a mag to drop, the trouble seating mags, limited holster options because of the pic rail making the dust cover bigger, etc, etc, I finally just sent mine in for the warranty swap.

Thanks for the info. I did notice that some mags wouldn't seat while others would. So far I have found ~13 that seat correctly, but I will have to check when I get back home if they have the extra indentation or not.

My G21 got back from Glock last night.  They swapped out he ambi release frame for a new gen 3 SF frame.  Serial number is different, not the -1 that some have reported.  They also replaced every part in the slide minus the barrel and sights.  All my mags seat and drop free easily now both loaded and empty, so for $45 shipping and an 11 day turn around I'm very happy.