As some other users said, disassemble (it's easy) and clean up all the contacts (with lots and lots and lots of good alcohol). Let it dry (after cleaning with alcohol) for about 24hours (not really needed, but to be sure no absolutely now liquid is left inside - better to let it dry outside the window, in a plate with silica gel packs). Check for the sliding magnet to be in place, put it back together and reflash (just to be sure).

If you still have problems, buy another slider, if the problem still persists... You have a hardware problem (because you used it while WET) and you can disable that function if it doesn't bother you, or get a new device.