Imported task remaining duration reduces after reschedule

I have an xer from a contractor where a 90 day Task Dependent activity with No resources comes in with an actual start date and 90 days of remaining duration, actual 71 days, at completetion 161 days and total float of 20 days.

After rescheduling the unchanged-imported project, the activity remaining duration reduces to 19 days, actual stays at 71, at completion reduces to 90, and the total float increases to 91 days.

How can the remaining duration reduce like this by itself?

There are no resources and no expected finish dates added. The only other clue is that the planned finish date from the xer matches the new finish date with the reduced remaining duration.