My 2019 Ventana 3407 has a "sticking" fan in the bathroom and can't seem to come up with the fix. It operates just fine all the time EXCEPT when someone is using the shower and there is an accumulation of steam in the bathroom. It will not open and requires I turn the thumb screw to get it open. Within an hour after finishing it returns to normal. I'm thinking a shot of WD40 might do the trick but wondering what is the cause and the permanent fix. Really looking to avoid disassembly if possible. Thanks all!