I'm going to need to investigate this a little more when I have sound. The way you implemented this would play a sound if any of the pushwall triggers failed (say remote switch that move many walls) and for each failure. Just briefly looking at this, I believe the correct thing to do is have a flag like doNothing which tracks if a secret trigger has failed. In that case, instead of using misc/do_nothing use player/usefail.
As a side note, this error seems to be somewhat related to issue #110. Although that might just need the P_ChangeSwitchTexture call to be an else to the if(doNothing).
I looked a bit into here and there seems to a bit more to this issue. If you look at the vanilla wolf source, the OperateDoor function in WL_ACT1.C indicates that player/usefail should also be played if you don't have the right key for a locked door. It is possible to confirm that this happens in vanilla, but you need to tap the button within one tic or the do_nothing overrides.
So with that said, I think the proper fix here would be to add a variable hasValidTriggers which is set to true before calling ActivateTrigger here and then using that to switch to player/usefail if doNothing remains true at the end.