I know this is a little "out there":
I have a crazed Custom Scientific V filter. A new one is on order from AstroDon.
Another project on the table is helping a friend fix his Lunt 80LT solar scope. He had left it outdoors under a tarp for a year and now it doesn't produce sharp images. He thought to send it back to Lunt to see what they can do, but Lunt told him a long pass glass filter (non-interference) can cloud up if it sees too much humidity. Sound familiar?? I was asked to replace the filter when it arrives in a few days.