A fun premise, but I get the idea the author was running out of ideas even before he clearly got told to wrap it up. And it's hard to write your characters so stupid, as if medieval people didn't have mirrors or abacuses. Also, I think there were enough pages to bullshit a conclusive end with all the OOPArts returned to their world, or shut down the machine that was teleporting them, but instead we had an open-ended finale and a big fight with a random vampire.
idk, there was almost something here, but I understand why it got axed. Author needs to level up and try again with another premise.