I had to look it up. It's a 35a controller I've had for 15 months. For maybe a year I didn't notice a problem. I see why. Some logic circuitry may be extremely sensitive to moisture, but throttle and PAS would quickly warm the controller enough that the circuitry dried.
About 3 months ago, I finally discovered that the proper tire pressure is 30 PSI. Rolling resistance is so much lower that I've reduced my motor usage by 75%. The controller runs cooler, and if there's moisture, circuitry may take longer to dry each morning. The first couple of miles is when the controller has sometimes failed to recognize a shift.
The bottom and sides are one piece, so there won't be a leak between them. The sides fit into slots in the lid, so that should be okay. The vulnerability must be at the ends. On the front, I saw that water could run through the rubber grommet on the cables. RTV fixed that. I saw that water had sat on top of the controller. I didn't know if the end plate gaskets were totally water proof along the top, but I added a little RTV.
The end gaskets don't fit tightly at the bottom. That was so crazy that I thought they were open for ventilation, and the designer knew that water couldn't flow up into the box. That seems to have been wrong.
With the grommet sealed around the cables and the end plates sealed on all four sides, I think my controller will be okay.