I've encountered a couple fun glitches lately, thankfully nothing game-breaking like the stupid matt fight I had earlier which was the worst (had to replay the mission 4+ times).
I was cleanin up the gang operations and on the southern left island (below the 3 Counts Casino) on some boats enemies would just respawn on top of one another. It got to be ridiculous. I flew over to the boats got "gang operation discovered" and then watched in humor as the luchadores kept spawning on top of one another eventually piling into a big mess. No matter how many I killed I couldn't get them to stop respawning...had to restart the game but it was still entertaining.