the game is going to be completely overhauled using a new decompile base and I'll try to fix the lag spikes you mentioned. events will only occur once for a run in the next update, so if you get mystery room once you never get it again in that run.
there are going to be difficulty settings in the game, I'll make it so in easy mode characters completely ignore the room itself, in normal mode they can see in it but can't enter, and hard/master NPCs can enter the room. in baldi's basics plus, in scenarios where the shop is present in a normal map (e.g. endless mode, register sticker) characters can enter so I think this is a good solution