Thank you very much for your detailed reply.
The scale is brand new, but I have NOT cleaned the parts. I will try that first.
The pointer is semi-sinusoidal, with occasional "catching" as you call it during decay. This does not happen all the time which could be causing the inconsistency. Makes sense to me.
I have already turned off the heater and all fans in the house, but I'll try the box trick if there are still issues. There is no binding or any contact with the dampner or pointer.
I'll post back with results. Thanks again!