I’ve seen this twice now, on todays sweet spot effort (donner) I noticed the first interval went on for quite a while. I thought ‘ok’, its sweet spot. Maybe RPE is a little high, not fuelled enough etc. During the break, I timed 30 seconds of a TR against my garmin stopwatch. This recorded 40 seconds. I aborted, bounced TR and tried resuming, same thing! I then aborted and went to using my iphone.
I’m guessing the clock in TR is not following ticks from the system clock? The laptop appears to keep time well (although ntp is on).
Usefully I recorded the interval on my Wahoo head unit, interval 1 is using my laptop with the time issue, interval 2 and 3 are using my iphone. This workout is available here for comparison; Activity | TrainingPeaks