Joe, That photo seems within specs, but any drift at all I would think should not happen at all.
I have noticed that when manufacturers include in their calibration sheet both temp and RH% when tested. Never have been sure about that. i mean you buy a multimeter calibrated in Cupertino and you live in Denver. both altitude and humidity is way different.
Mine has been modified and may not represent how a stock meter would behave. With no leads attached, selecting the mV function, it will display OL and slowly drop. Of the meters I have looked at, this meter was one of the worst for temperature drift. One of the things I had done was compensate mine. I would have no way of knowing the tolerance of your 30V supply but I have been tracking the drift. I have attached today's data. The voltages are checked against a Fluke 731B reference standard. The 100ohm is a 0.01% 2ppm Caddock part. Capacitor is a COG.
Attached picture shows how badly this meter has been treated.
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I have watched your videos on modding multimeters. I wondered about is, if changing out MOVs, didn't the calibration change?