Seepage boss teleports you outside arena

I did a Seepage map, and encountered the 3 monolith things that spawn a random boss.
It chose to spawn the Fungus Behemot, which is the same boss as the final Seepage map boss.

When fighting the final map boss in its arena, it did its teleport attack that is supposed to move you instantly in the middle of its arena where there is explody mushrooms.
It instead teleported me halfway across the map, where I fought the previous random boss from the 3 monolith things.

It might be due to the location of its "spore cloudy thing" that seems to indicate the target of the teleportation, maybe it didn't disappear ?

Anyway that is a rare occurence as you need to have 2 copies of the same boss in different places of an instance, but it was annoying.