Have the same problem on Dead Man's Booty endless level 64, all enemy waves ended, but my plants in row 2 from bottom keep firing to the other side endlessly with no enemy ever coming out.
Same problem here in level 101 of Dead Man's Booty. There is something invisible and indestructible in the rightmost plank square in the 2nd row from the bottom that my plants insist on firing at ceaselessly. I can see the impacts hitting what appears to be thin air. Whatever is or is not there never dies, though, so the level never ends. Unfortunately, I am also provided merely with the options to "save and quit" or "continue", so I can't restart.
