You can only wind a spring drive clock so far and then either the spring will break, or the key will break, or one of the gears will be ripped loose. I have seen some clocks that have been forced so hard that the arbor actually has snapped. The old Urgos spring drive clocks have an arbor that has a small groove cut in it for assembly convenience that will snap if you force it. If a clock needs repair and it is wound fully many times the mainspring will stick. This gives the appearance of the clock being wound too tight. Essentially , from the users perspective , it is. From the repair person’s point of view it needs cleaning. Each coil of the mainspring has only a fraction of the power of the total power of the mainspring so if the surface tension of the mainspring grease is to the point where it does not allow the spring to release ( because oil / grease thickens up over time and becomes “sticky”) then when the mainspring is wound FULLY all the coils stick together and give the illusion that the mainspring or clock is broken. It sort of is, but not from over winding. If you over wind a clock and break it , believe me you will know. You may loose finger nails faster that you can see , there will be noise with a volume directly proportional to the size of the spring.

On weight drive clocks, often the pulley/pulleys will catch on part of the mechanism or mechanism mounting hardware if the clock is fully wound and give the impression of the clock being wound too tight. Also, the cable can come off the pulley and get stuck between the pulley frame and the pulley this may prevent the associated gear train from functioning. These are things to look for.