The E-Gas level can be wiped off with a damp cloth.
When inserting the E-Gaslevel, make sure that the rubber cap is not damaged and that it does not shift during use. This cap is necessary for data processing and cannot be replaced. A damaged cap will render the sensor unusable. If necessary, sand the underside of the gas bottle lightly with a sandpaper to remove any unevenness.
If necessary, lubricate the rubber with some dielectric grease (e.g. silicone grease/tap grease) before attaching the module to the tank. This can enhance the signal a little.