It's a bit long ago now for me to remember the details accurately but isn't there an air pipe that gets disconnected every time you do a comp wash in order to prevent water getting into it?
I have half a recollection of having to very carefully check that (a) it had been done up again and (b) it hadn't cracked with repeated daily on/off handling.
Please excuse if this isn't relevant.
Cheers
JerryG