Chris Bennetts wrote:
[...]
Why is this so strange? There was no particular reason to fire the
engines since Zvezda became part of the ISS complex, so they simply
weren't fired in that time. More recently, somebody decided to test them
out, even though there was no particular need for them.


I think that there are constraints on when these thrusters *can* be
tested, since the presence of a Soyuz or a Progress at that docking
position means the other craft gets contaminated (at best) during a
firing.

It was noted that there was a period with the docking position clear,
enabling the test, and that the next opportunity will be September.
And that no retest is planned for September at this time.

I think the reason for conducting the test was probably entirely innocent.

Maybe.


/dps