Time dilation. The ISS travels at 17,400 MPH. Just like satellites, their clocks have to be adjusted.

> Gravitational time dilation is the time passed for a far away observer. That is, the satellites' clocks gain 45850 nanoseconds a day due to gravitational time dilation.

https://www.gpsworld.com/inside-the-box-gps-and-relativity/

So the astronauts are perceiving that everything is a few minutes older than it "should be" when they return?