Simulacrum doesn't allow continuing to next wave

Multiple times now, after finishing a wave in Simulacrum, the functionality breaks and I cannot continue to further waves.

Sometimes, the npc and the popup box about the Sim is there, but cannot be interacted with.
Sometimes the npc and the box vanish entirely.
The doors to exit the "room" to move around the larger map remain closed.
It hasn't moved to the next room and even if it had I can't leave the current room to look for it.

It is not consistent what wave it happens on.
I'd had this happen as early as wave 4 and as late as wave 13.
It also happens regardless of whether or not I've died in that run of Sim.

Stuck just staring at the unclickable npc, or the spot they should be standing, taunted by the fact my splinters have been wasted again.