In the fight lesson between Mex and Cyrus. Mex punches Cyrus in the face which result in a nose bleed. A couple of frames later the nose bleed is gone. But it reappears during their dialog later.
The man jumping over walls during the foot chase is very obviously not Reynolds.
When Cyrus jumps in front of Nick to shield him from being shot, the bloody squibs are showing on Peter MacNicol's chest before his character is shot.
Scene in Baby's office where Nick is "on trial" for murdering DeMarco's henchmen, mid way through the boom mic drops into the scene briefly.