I purchased a used boat that came with 2 NavNet VX2 units. I am still trying to figure out which models, how to upgrade software and install chip, etc., but right now I have a more pressing issue, which is the screen on one of the units being very, very difficult to see. It has what appears to be "water spots" on it for lack of a better description. They do NOT come off. So far I have been gentle - a little soap and water only, then a try with a little vinegar and water, all with high quality micro fiber cloths. The spots are not fazed in the least bit. It's like they are under the glass, even though they can't be. The screen has a purple-ish color to it which I assume is the anti-glare, so it is still intact. There are no scratches or other damage, just these spots. Does anyone have any advice on how to get these off without ruining the screen? I assume I can't be the only one to have had this problem but in searching here and elsewhere I cannot find an answer. It drives me crazy, so I hope someone has a tip. Thank you!