Diagnosis
Mud and water around the deck seams can ingress into the battery compartment or controller area.
How to Fix It
Use a damp cloth only. Wipe the deck top and underside. For the underside, avoid direct spray. Use a soft brush to dislodge dried mud. Critical: keep all water away from the deck seam where the top meets the sides, and from the charging port cover.
If That Didn't Work
For ingrained grime, use isopropyl alcohol (70% or higher) on a cloth. It evaporates quickly and is non-conductive.
Heads Up
Never use a pressure washer or hose. The IP54 rating is for light splashes only, not directed jets. The deck is not fully sealed.