That slide release/lock should work in and become easier in time.
The compacts have more spring tension, especially when brand new. Put some rounds on it and it should wear in nicely.
If it is still giving you trouble after a few hundred rounds, clean up the lever interface where it engages the slide. There may be a lip/burr/roughened area that needs to be touched up. Just go slowly with a very fine 600 grit paper or stone. Test it out as you go, it won't take much. Don't go too far!

I know there is debate about the use of the slide stop, mostly from Glock based trainers. Releasing the slide with your support hand by engaging the slide release/lock is just fine IMHO... and usually faster. I prefer it as long as it is consistent. If it isn't consistent make it so.