MVP-8400 loosing calibration

informel

every now and the the panel loose it's calibration and because it is way off, I go to calibration mode using the web interface; then I can calibrate it and it will be OK for a while

firmware is 2.85.14 (latest one).
I had some error concerning the battery a while back, but not receiving any bad message lately

I do not remember if it start doing this after a firmware update because this is my demo and I alway recalibrate it;

panel is about 3 years old now

Krobar

I have seen MVP-7500s that do the same. Calibration gets worse and worse, parts of the screen just stop working until I calibrate them again. I wonder if the 2.84 firmware was involved but dont know for sure.