Built my first AR... Spikes lower with a Delton upper (bare with me if i am using the wrong terms, I am still a newbie)

First two mags of brass 30 rounds fed fine. Then I tried Tula, and it had problems feeding.

It happened all day and was very frustrating, but i tried to stay positive and turn it into a learning experience.

Here are the symptoms:

The ammo would start feeding into the ramp but get stuck. Almost like there was not enough to cycle the bolt entirely. I can push the fwd assist and sometimes it would finish the feed.

I noticed the mag was not entirely seated sometimes when this occured so i slapped the mag and it fed fine. So i tightened the mag release one spin (but now the release is no longer flush with the mag release button, is that ok)

Still was doing it, tried multiple mags. Even on brass it was having this problem.

Could it be short stroking? Any ideas would help and again i am a newbie.