Sokki DL102 digital readout

My Sokki DL102 readout and scales were purchased on ebay years ago,
they've given good service, until now. The display reads FF.....,
which according to the manual might mean overflow. This must be an
error since nothing is moving. This reading comes up on both x and y
as soon as the readout is turned on.

No pushing of buttons seems to change anything.
No changes have been made in any settings.

I've checked the power supply, it gives +5 and +/-15 V as one would
expect.

Connectors have all been pulled out and replaced.

Does anyone have experience with this brand, or know of a
repairperson? A web search was not helpful.....

Any help would be gratefully received.

regards-
Elliot B.