The drier started getting used again, after 2 years.  The apartment router briefly resumed logging hygrometer data & then it died.  It seemed hardly worth the effort of troubleshooting the radio.  It had a very constant range of dewpoints.

Clear TPU proved very hard to keep dry.  It only manetained an equilibrium in the solar drier.  Decided to leave it permanently in the drier & let it turn brown.

Something needed to be done to improve the effectiveness of the desiccant, starting with getting rid of any kind of cover.  A new idea for storing the desiccant was an erlenmeyer flask inspired container with 2 holes.  Wet air would be forced in 1 hole so dry air emerged from the other hole.  The same fan should circulate air around the filament.  There wasn't enough room to fit such a flask in the drier.  

Eventually settled on a tall desiccant bin from a 50oz soap bottle.  64oz soap bottles from 10 years ago would be too wide.

Helas, the tall desiccant bin requires the container to always be stored vertical.