I have 60# solenoids and still have problems as you do. I have rigged a small umbrella made of plastic to shield the top of the solenoid. It works most of the time. I also took the solenoids apart and drilled holes inthe lower plastic base so the water drains out and it is vented. This helped some more.
However the whole system is unreliable at best. It is so bad that I have to leave the window down enough so I can get my arm in to release the door if the FOB doesn't work. I finally do have a mechanical release. But why do I have to have this???? my truck has electric locks and they have not failed in 13 yr and 270k miles.
Frankly I'll never do shaved doors again. After all how many production cars have shaved doors??? It will be far better to mold a nice door handle into the door. I have very thin doors too but I'd go to the effort to cut a small opening and glass in a mount for the opening rods.
I now have only one FOB that works and I'm told I need to buy a whole new system to get new style FOBS as mine are obsolete. They are only 5 yr old and now obsolete???? give me a break. I can still get new /FOBs for my 13 yr old truck and from Dodge no less. Aftermarket needs to make stuff for us that use their products for more than occasional use show cars.