Bit of an update.
It getting cooler here now.
Last week we went away for a few days and upon returning I noticed some water in the pipe and quite a few dead bees, looked like they had drowned.
It appears that condensation was forming in the PVC pipe near the entrance, and dripping down and collecting just before the entrance (right above the notebook in the picture).
The hive itself did not have any moisture on the glass or damp spots below the bottom frame.
I removed the pipe and cleaned it out. In the morning the moisture pool was back, and bees not happy at all having to cross this small lake. And more drowned.
I drilled a few small drain holes in the low spot and all is well again.
Has anyone else observed this problem? I suppose I could ensure that the entrance to obs hive is higher than the window entrance so any moisture would flow out?