Mole warrior prevents towers from shooting when swarming. Bug or feature?

[Bohimen]

Hey all, I seem to be stuck on 13/14 of let left most bonus level (the one where you get the Power Tower, Elite Tower, and Archery Gfills(?) when the Elite Mole Warriors begin to swam. Basically once they get on top of a tower, the tower seems to stop shooting for some reason. Considering they can b-line the castle if RNG is not on your side, and I can't command my troops, this seems way harder than perhaps intended.
Let me know if this interaction sounds like a bug.