Iron Brigade is another example, sort of a steampunk/military action td game. Even though it's fairly different, Yet Another Zombie Defense HD might scratch the same itch and it's on sale for $0.51 right now.
If I'm being real:
popped up in my sub feed on youtube. She's from my neck of the woods, I've actually met her brother who played in Silvertide and Shinedown!
I've only had this happen to me once on wave 24 of promenade NMHC. Otherwise, it's never been an issue but I haven't run glitterhelm yet. They eventually came out of the spawn door when it happened to me.