Mark, I can't speak for Rick, but I'm not talking about during calibration. I just calibrated all of my hygrosets within the past three weeks or so at room temp (70-75 degreres).
I experienced this when I got home today. I pulled one of they hygro's out of the wine cooler and it read 71% and 66 degrees. I watched it climb to 67 degrees at which point it read 69%. A few seconds later it hit 68 degrees and immediately it dropped to 64%. Doing it again while I type. 70% and 66 degrees....69%, 67 degrees........................................................................................................damn. 68 degrees and 64%, instantaneously.
I just swapped places with my other hygro (higher temp at the top of the winecooler so I'm waiting for it to drop below 68 degrees.
(OK, so I'm going to have to come back to this one, I can't sit around waiting for it to drop to 67 degrees, I've got to head out soon)...
Just pulled out my circular version, same thing. 67 degrees and 66%, as soon as it went to 68 degrees it jumped down to 61%.