haven't heard of it before. is there a crack any where or been mishandled like took a fall or some thing?
do you use the snow shield? did it get wet inside the unit or a lot of water get on the actual display screen because it didn't have the snow shield on?
the display screen is just like your monitor or smart phone screen or tv. if you get water under the glass, then that could happen for sure. the head unit has a water proof gasket and when i had mine apart i couldn't tell what they use for the frame to screen area for water, but it acted like adhesive of some kind.
being the edges of the screen are inside the head unit, it would or should be hard to get water behind the glass. i get splashes of water on mine after tossing fish back and at times the snow shield is off of mine. i think the edges had a wrap around them too. so it sounds like environment is causing it. it's not a common issue tho at all.
maybe extreme temp differences are causing a condensation issue. maybe the humidity from your home to outside is causing it.
toss some silica packets into it. the rubber flap should be an access point for them.
try to remove the moisture by sealing it in a air tight back and use crackers and rice. try to remove as much air as you can before closing it up. it takes a long time like a week depending on whats going on.
i would set mine in front of a heat register to try to dry it out first thing.
could always call the ones who know best.
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