What's this thing glitching into the warehouse?

[gloomy spindle]

there is a known bug that rollerboi remains will 'grow' to massive sizes if you don't dismantle them right away.
did you kill a rollerboi outside or in another room? if so, it might be him

[knotty oasis]

Will it break my save if I don't do anything?

[gloomy spindle]

i suggest reading the post in the support forum titled "Rolling boi' increases in size after being killed, getting enourmous"