Sump map ritual encounter not ending

Just the title, nothing special.

Additional info: There isn't any mob like the vaal robots, fire golems, etc... that require you to go near them so they become attackable.

I spent few minutes walking in the ritual, trying to step on everything possible.

Teleported few times in and out of town.
At some point it just ended... Like 5 minutes or so, give or take few.