I'm not sure this has been captured on video before, but last night while streaming my TMNT Premium I had the issue of 4 balls being loaded into the turtle van. It happened multiple times throughout the night. Here's one instance where I reset the game and it immediately loaded 4 balls once it booted up. Reset it again and then it wouldn't empty the 4 out of the van so I had to take the glass off and manually release them. My theory is while in turtle power multiball, once the ball saver runs out it reloads the van, but sometimes while loading if you shoot the right ramp at the same time a ball is being loaded, your shot to the ramp and the loading ball both enter the van...confusing the game.
https://www.twitch.tv/videos/770121929
And here's another instance of the game loading 4 balls during Turtle Power Multiball.
https://www.twitch.tv/videos/770130608
Oh, and I've now been waiting 2 months for a replacement glider mech from Stern....