Hi my name is***** a car technician and I’ll help with your question.
Did you have your original dials adapted or a new replacement set fitted?
Ok so if these are cover dials which simply place over your old dials they certainly should read correctly. Do you know if the needles were removed to fit the new dial plates? Some are cut to avoid needle removal where as some aren't. If the needle has been removed often damage can be caused to the driver motor which moves them as they are very delicate.
I strongly suspect they were heavy handed with the removal of the needles, and this has damaged the spindle in the driver motor. If this is the case the entire motor/dial assembly can be swapped from a spare set to yours to retain your current millage. I understand that you don't want to change the entire unit and loose your millage
No problem. Good luck and feel free to ask if you need any further assistance. Thanks, Ross.