Doubt you're seeing a correlation at all with the specific design of the Copal, just with its potential age & wear n' tear. Copals are rarely or ever accurate at the highest speeds, but most LF photographers never use top speeds anyway. I test every single one of my lenses with a shutter tester. The older Copals have been just as accurate and predictable. You just want to be aware of condition. Sometimes old shutters can stiffen up with inactivity over the years in storage, and need a CLA.