WMR200 intermittently reports 52ºC - but only at night

[adamjackson]

Anyone recognise this WMR200 problem (see screen shot)? Both my THGR810 temp/hum sensors intermittently report 52ºC (or -52ºC), but only in the history data produced overnight (when computer and WD are turned off). Beginning to wonder if it's a null reading thing, like UV=255. . .
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Red trace shows one sensor read high all night, the other intermittently. Today the problems roughly coincided with shutting down and restarting the computer, but this is rarely the case.
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