Can't use the lader to go up.
I can't search Mr Quidam in one the scenario.
Could you tell us which scenario and particular fight you're talking about? It's hard to help with that little information.
As for ladders - maybe you know that already but you don't have to click on the ladder itself but rather instantly give a move order to the destination tile on the other floor. Make sure you're standing not too far away from the ladder before giving the order, so you have enough movement to actually finish climbing the whole ladder in one turn.
If that doesn't work and there's actually a broken ladder somewhere in the game I'd appreciate more information about its precise location so we can take a look at it.