Before getting my 20s evo in June 2018 I had a good look around and checked out all reports for reliability and problems, one that came up time and time again was with this unit failing in heavy rain.
Now up until last weekend I had been out in some realy bad weather with no problems whatsoever, this all changed on friday coming back from Wales in a wee storm, and the problem was found as soon as I returned home, ok so when the 20s evo first came out the seal between the mounting bracket and the control unit was made of foam rubber, water would eventually get into the connector
and this is where the reports of water problems came from, on further investigation I find that Sena modified the mounting bracket and seal but not many people know this, I only found out by checking a new mounting plate I had just fitted to another helmet, and below you can see the difference between the two seals, the second has a rubber sealing ring around the foam inner.
The old seal
The new seal