HP-67 Charge Issues

[dcs]

I have an HP-67 question, regarding behavior while connected to charging power.

While on battery - it functions normally.

While on charge power (original HP power supply, rebuilt battery pack), the display flickers and key entry is very erratic (example: keypress of '5' results in '5555' on the display). Unusable.

I seem to recall being able to use it while plugged in (when I first obtained it), but am starting to doubt my memory.

Does this behaviour sound familiar to any experienced HP-67 users?

Thanks in advance for any advice.