1. Give us the steps to reproduce the bug

Exert an exert creature (in this case, Basri, Tomorrow's Champion) on own turn with Prop Room (of Dazzling Theater/Prop Room room enchantment) active on the field.

1. Note which platform you’re using (PC, Steam, Mac, Android, or iOS)

PC

1. Enter the actual results you’re experiencing

Turn passes to opponent, all my creatures except Basri untap on opponent's untap step. Also does not remove Basri's exertion (this is not the expected interraction, but would be how it would work if it were a stun counter, or alternatively if I were coded to have an additional partial untap step on my opponent's upkeep).

1. Enter the expected results of the feature

Text of exert: "An exerted creature won't untap during your next untap step."
Text of Prop Room: "Untap each creature you control during each other player's untap step."
Rules as written, exert should not prevent this untapping. Getting around exertion with untap abilities works as far as I know, so the issue seems to have something to do with that Prop Room is not a triggered ability, just an action that happens during the untap step.