Label timestamps way wrong

Am using 3.7.5 on Win10. I find the timestamp on exported labels is way off, 1,2 minutes (out of 8 minute track). It seems to be associated with deleting some section of track.

BUT it is worse.

I make a label, export. Save/close/open project. Then move the label forward/backward, export again, and the two exports have identical timestamp. I can change label name OK.

Any solution? Otherwise exported labels are useless.