Chong, Yea have heard about all the issues from 8 round mag being different size, mag release spring being too week. I had the issue. A pal said he put a stiffer spring in mag release button and it helped. I didn't want to mess up my 1 year warranty. I called Kimber. They said send it in. Shipped to Kimber on Wednesday 3/27, arrived 3/29, shipped back to me Thursday 4/4, arrived at my house 4/5. So first let me say wow they don’t mess around.The reports shows they replaced the mag release and tested 4 mags through it with no issue. They also replace slide stop and spring as a “courtesy”. Not sure why but works for me. when inserting the magazine it’s not the same. When the mag hits the release catch you can tell. Prior there was very little resistance. Magazines stay put until released now. Call first to get RMA number-Toll-Free: (888) 243-4522

Chong, sounds like the magazine catch may not be fully engaging. Are you getting an audible click when the magazine is inserted? Once inserted, does it come out with a good tug? If it does then the magazine catch may not be properly retaining the magazine.

Weird, and you’re sure your thumb isn’t engaging the mag release. You may have a lemon. How does it shoot if you use one hand? Have you tried shooting it with the regular mags? You may have to send it back to Kimber.