I was able to recreate the glitch, it seems the towers need over 200 range to create this effect.
Laser/broken-rocket-tower combos are sweet, because the rockets will never explode, so they are essentially multiplying laser cannons.
I found a really cool glitch which I'm trying to recreate:
on the classic map I put a rocket tower near the entrance so that it's basic range covered the upper loop and the entrance paths. I figured that since the rocket was destroying everything that came near it without help I'd just keep upgrading it, however when I upgraded it to the point when it's range exceeded the boundaries of the map, the rocket tower just started firing missiles continuously even when no enemies had spawned. The rockets, having no targets circled around idly, however whenever an enemy entered the towers range, all of the idle missiles would lock onto it, and they'd do this continuously until everything in that wave was destroyed.
This glitch allowed me to reach wave 63 while only relying on one, incompletely-upgraded, rocket tower.
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