William - we do appreciate you bringing it up, but the best place is over in the other side so that we can get to the root cause.

Here's what I know now: There is handling introduced into MaxIm 6.21 to handle cameras that have their own ability to precisely set the DATE-OBS time (eg those with a GPS-locked time stamp or other high-precision timing mechanism) that is likely involved in this.

What I'd like to have from you is what hardware and driver version and/or plug in you are using so we can try to track this down quickly. It may be that the driver for your hardware does not implement Camera.LastExposureStartTime or that we aren't handling it right, or some other possibility.