OK, great news: the antenna was unplugged. So that explains everything.

Also, the lid warped in the sun & cold and the caulk was insufficient to hold the seal as a result. Seems like there was no water damage though. My notch & grove design seems to have saved me.

What I learned:

- put tabs on the box & lid so they can bolt together (which I already did and will be on the next print)

- don't use caulk for strain relief because it may have already popped off before you get that far

- assemble & and caulk them inside, not on the roof at installation time

- test them fully assembled & sealed on the ground first

- check back frequently after the initial installation to see if there is warping, if the caulk is holding, etc.