I just looked through my repair tips , maybe relevant

Ferguson FV21
Manual record and short lead-time timed record OK but failure
of overnight record.
Replaced the the 3 small electrolytics on the clock / timer panel
and broke / inspected /remade all connections and
also at someone's suggestion tightened all earthing point through-pcb
screws on the various boards.Somewhere along the line must have
effected a cure.