My e-bike uses a very common Chinese controller with a display that has a single M button (see picture). It’s covered by a thin plastic membrane that wears out over time, eventually exposing the micro push button underneath and allowing dust and water to enter the circuitry. This design lets you fully replace that button. I recommend printing it in ABS or PETG, as these materials are more resistant to weather and environmental conditions. Just put some glue on the housing and hold it in place .