I have corrected the bug and you can now enter the second floor and beyond...
It works, it's just so difficult it makes fighting anything out of the question, which wasn't the case before (last time the spider died quickly, now they take many hits). Things out-dps you so I have no choice but to run away instead of loot chests. Sometimes it puts you back at the first floor and duplicates the level when using stairs.
Yep don't think this is a browser bug
I was able to replicate the bug on Chrome
It is caused by clicking on a staircase the clicking on the other staircase, queuing system gone wrong.
Sorry about that refresh the game and it should be ok.
Will fix this and other bugs before "version 2" release thanks for beta testing :)