I'm almost certain it's the Steel Tower objects. Been noticing it causing issues in other places recently.

@claude_dubille unfortunately it just seems to be an issue with the blueprint, I asked the devs on reddit and they can't explain why there's a problem either - I emailed them it so hopefully they'll get back to me on that eventually.

Nice ER! Very good, but I am having trouble placing it. It keeps saying space already occupied. I've checked the terrain and other standup coasters.