We call it "seal creep" and had 4 repaired locally for about $800 with a 5 yr warranty. It was cosmetic on our MH. There wasn't any fogging/moisture between the panes. We had it done when the paint shoppe had to remove the windows to paint the coach. Once we delivered the windows to them, the glass company had to pull the glass out of the frame, pull the panes apart, clean the glass, install the new seal, reseal the panes together while putting a dry air vacuum on them, then put them back in the frame.
The glass guy explained that there is a small chance they might break the glass when taking them apart $$$$
There is a place in Florida that fixes such problems. You'll have to ship them your windows. suncoastdesigners.com
I don't recommend the company that did our windows, because they were a pain to deal with.
Hope this helps