OK for fair-weather road trip but nothing for rain / mud rides

I have bought this lamp to a small, lightweight taillight dabeizuhaben, if it is on a mountain bike tour times later. After the first trip the muddy part went out to vibrations on / off.
Short cleaned. OK lights up again.
11 km riding in the rain and the same effect. In the middle part goes out.
When cleaning try the thing disassembled into its component parts. O-ring, red plastic, still an O-ring. Was a slight Frickelei to assemble the part again.
Come on now in your backpack as a replacement lamps or to the city bike.

Pros: small, light, super bright, can be attached quickly to the seat post and settle as quickly (always take with you when you are allowed the wheel!)
Negative Punk: does not tolerate moisture, you must first click through the different settings until you get to the continuous light. A bit annoying. The other way around, I think it would be better