It is something I have noticed on a rare occasion and have reported it to Bering Optics with my prototype Super Hogster. I honestly didn't notice it with the eyepiece during this hunt, but have before. It was very windy, and the wind was coming from the right side, so not sure if the sensor is picking up something that is causing it to "strobe" a little. I have my battery on the right side of my rail, so it might be getting a little reflection from it as well.
Thermals will adjust as the thermal is moved. You will see thermal images change as you get to the crest of a hill, nearing the horizon, drastic changes in elevation, etc to get the best image. It is not unusual to see some shifting in the image. It may be as simple as it needs to be NUC'd but I wasn't about to do this with 2 coyotes coming at me. The other possibility is the sun was setting and the moon was rising during these stands. I could have been getting some reflection from either as I know the sun was off to my right side.