LX7000 igc-Pro altitude reading

Today our LX 7000 behaved strangely. We had hi pressure, 30.49".
I set the machine as we normally set it at KAWO, 137 ft, and actual
QNH of 30.48
While we were flying, the LX 7000 reported altitude was consistently
450 to 500 ft above the Altimeter.

Later while on the ground at 137 ft I checked the altitude and it
stated 468 ft.
I rebooted the LX7000 and reset it and again the recoded altitude was
460. and this altitude was reflected in the glide-slope calculation.
It showed I need 320 ft less altitude that I should have needed.

Now comes the strange part: I checked another LX 7000 in another
DG-1000 and it reported 460 ft also while sitting at 137 ft.

Any suggestions?
Heinz