For me it happened right between the room of the bull Boss and the Save nest before it. I did a quick "enter room and go back immediatelly" because I wanted to record the boss (for no particular reason, really, I just like doing that) there and then I clipped.
Since a lot of other people seemed to report clipping into the Backrooms too I assume this can happen anytime you swap rooms too fast tho, but that I can't say for sure.