Charger reading false voltage

[badger5]

I have an Ansmann Xmove 2 charger which has just started to read the wrong (low) voltage for the first cell when charging and discharging, I've tried different cells, charging leads and balance boards and all give the same fault, all have been with 2S. The voltage of the first cell is always 2.8-2.9 volts when the true voltage is actually higher, the second cell reads correct and the total pack voltage records ok.
As the first cell is measured under voltage the charger won't charge the pack.

Can the charger be repaired or adjusted so that the voltage is measured correctly? Or will I have to buy new?