St2 display failure

Moin together, since our car is broken, I had to drive to work with the mopped for the last few days. There the mopped is unfortunately also outside in the rain. Yesterday, when I started the ride home, the clock went through the display in a quick run. Like when you set the clock. Temperature indicator remained on LO and the tank indicator also showed no movement. Even when ignition, the whole stuff continues. I checked the plugs of the two temperature sensors. Nothing oxidized or Finally I solved the red plug that comes from the display and I am without the display to work. After work the plug again and everything was good again. After two minutes drive the misery went off again. What could the error be? Water damage in the display? Since the error is also there when ignition is off, must be somewhere a short circuit, right? Thanks for helpful tips.