that is because the switch is too close to the door. I, at one time, consitered using "plrcanbeseen" everytime the switch was used... but that (I THINK, may be wrong) is an enemy only command, and would have to be adjusted to allow it for regular entitys.
Perhaps it is allowed for all... try it!
Either way, easier is just to edit the door script
like so...
:state=0,activated=1:state=1,setframe=0,sound=$0
:state=1:incframe=0
:state=1,frameatend=0:state=2,coloff
(if there is no 'activated=0' then it can't revert)
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