Looking for ideas please.

My wipers will simply will not turn off unless I turn the key off. Annoying!

Everything else about them is perfectly fine. They initially turn on only when I want them, they set to the speeds I want, etc. If I turn them OFF, they behave as though I set it on the slowest intermittent setting. I have to shut the key off and back on in order to make it stop. Madness!

I have checked fuses. I have tried swapping relays (at least one relay in the main box is for the wipers, so far as I can tell). All to no avail. If anyone has insight on what else to try or look for, that would be great. It really seems like a stuck relay issue to me... but I dont know where else to look. Or, what else could it be?

2001 Expedition EB 5.4L 4x4