LC9s Slide Locked back and slide lock release

It's happened to me a couple of times. While shooting the slide locks back. I pull the slide back, hit the slide lock, and everything is fine.
I think I'm causing the slide to lock back. In my grip, my thumb is just under the slide lock and I think the recoil is causing me to hit the slide lock up into the locking position. I will have to keep my right thumb lower when gripping the gun. I have no trouble with my other pistols but with the LC9, my thumb seems to creep up too much.
The second part of this problem is releasing the slide. Pushing down on the slide lock varies from gun to gun, as does the opinions of what's best. With some guns, I can just push down on the lock to release the slide. With other guns I can release the slide by pushing down on the lock with my thumb, but it take a lot more effort. With the LC9, I have to push the slide back with my left hand before I can push the slide lock down. I was wondering if this is normal and if anyone has done a little filing on the slide or the slide lock to make unlocking the slide easier?

Having to push the slide back before/during release of the slide lock is normal. This is covered on page 22 of the user manual. The LC9s is NOT a 1911-style pistol. If you try to file/alter the slide release you are simply asking for a lot of trouble.

I agree, if you take metal off ... it is really really hard to put it back. I'd suggest working on your grip and when this happens just use your support hand to pull the slide back, release and sling shot the next round into the chamber.