To get Backrooms Chomik, you need to access multiple different levels. This seems fine at first, until you get to Level 28 (Stormstone Keep). Level 28 has a key, but is not connected to any other levels of the backrooms, and therefore without the use of fast travel, you can't leave. Not only this, but there are no levels that allow you to enter Level 0, which you need to enter at the end of the run in order to obtain the chomik. In my opinion, there should be a rule that allows you to use fast travel to either levels you unlocked during the run, or only to Level 0 at minimum. I am looking forward to doing this run, so I hope this can be fixed as soon as possible.