Originally Posted by GhostMutt

Regarding the bolt not holding open or closing properly...the problem may be with the bolt latch itself....it may either have crud in the channel where it moves or if memory serves me well the issue may be resolved by clipping a coil or two from your bolt catch spring. (type bolt catch spring into the search tool on this forum and it will bring up some threads related to this issue)

That being said (and by typing the following I am in no way trying to diminish your abilities or competence)...but this issue did not happen before you did your cleaning of the mags....maybe try turning the mag spring upside down and checking that your follower is placed in the correct orientation...always look for the simplest cure before performing unnecessary surgery.
Apparently some of the followers were released upside down from the factory.......lol This guy in the video is really safety conscious....How you make a 10 second vid into a 5 min one is evident here.

M&P 15-22 10rnd MAGAZINE FOLLOWER FIX - YouTube