A bit of advice from the font of knowledge known as Tweak-
Check your carrier key and gas tube for a spent primer that traveled...
From my personal knowledge base- Check to see if there's anything binding in the buffer tube. Also check the spring itself, and the buffer for any burrs. Check to see if the lip is aligned with the lower (Where it screws in) as well as the hright position of the buffer dentent. Make saure nothing is mashing together there(Shiny spots).
Past that- run a 17" mop (Pipe Cleaner) saturated with Hoppe's #9 down the gas tube, then run several dry ones.
(Another helpful hint, is that I have used blanks to check function...works pretty good as long as your FH/muzzle device supports mounting a blank firing adapter (BFA).
ETA- Just re-read your origional post- Try tightenting your Mag release up a turn or two. Push in hard on the release from the right side, grasp the arm on the left when it comes out, turn clockwise 1 full revolution. Check function, if that ain't it, repeat. If that still ain't it, put it back the way it was and continue to trace the origional symptoms.