I would suspect that they have lost the settings perhaps because the system has been off for a long time, however, if they have non volatile memory i.e. flash then other possibilities are that setting data from the plc is not correct, this can happen if the plc battery has drained, someone perhaps replaced it but not configured the data. I helped someone last year who had the later version Mitsubishi (Q) series, this had a number of motion cards, the main problem was to do with divide by 0 as some setpoints were zero this was due to some code that zeroed virtually all the "R" registers, we believe this was a deliberate attempt as there were conflicts between the customer & the supplier of the bespoke system who actually walked away from the system, I did the diagnostics via a remote connection, I did notice from a quick video that the servo cards were flashing but at that point ignored them due to the PLC problem, I only diagnosed the problems with a number of registers that were causing the plc error, I informed the customer they would have to play with the values to get the servos working correctly apparently they did this so the servos were ok.
This is a major problem with second hand equipment, often slod without drawings or backups of vital software or settings, often equipment that is too old to be sourced easily or the original manufacturer has gone out of business, bespoke PC programs controlling plc's again is problematic, if the software is too old to be installed on modern operating systems then again sourcing old pc's or OS can be difficult, I would certainly not buy second hand equipment without all relevant manuals & software or with components that have been discontinued for many years.
