RSS system alerts with no obstruction

While this isn't an issue specific to the 6.0, I didn't see an area it seemed appropriate. Anyway, I have the reverse sensing system on my Excursion. It has worked just fine until the other day when I had to go through a lot of water and it was about 5 degrees F out. Ice accumulation EVERYWHERE!!! I spent about half an hour at a heated water high pressure wash place to remove several inches of ice off my undercarriage. Anyway, before I removed the ice I put it in reverse and, of course, the backup alarm was screaching like mad. I figured after I removed the ice from the bumper it would be ok. Not so much. Even with clear sensors it is still screaming. I'm figuring there must be some water in them or in the connector, but I've never heard of this issue before so I thought I'd bring it up here first to see what the community might have to offer.