Willard responded with a suggestion to change the mainspring.That's an odd one. I'd check over on ST to see if Willard might have some idea.
So I went ahead and ordered 3 of the red DAK mainsprings (in case other DAKs I have may have this problem), OEM Part # P00156 from Top Gun Supply this morning.
They're coming UPS Ground as the USPS where I live isn't dependable.