Altitudes and altimeter instability with ATC

ATC is really unstable. It will tell me to go to 14,000 ft, and 15 seconds later to descend and maintain 13,000 ft, followed almost immediately by going back to 14,000 ft.

Same with the altimeter…29.74, then a minute later 30.35, then back to 29.8, and on and on.

I’ve seen this when flying over mountain ranges, once when approaching LOWI from the SSW.

This is what I’m talking about…this is only a small portion of the ATC communications: