In my last Current Events presentation I mentioned the reverse positioning of the ISS in the Solar transit images of May 24 and 25th. I send an email to NASA and got a reply. Here it is:
Sorry for the delay in getting back to you on this.

ISS can maneuver to change its attitude (i.e. rotational orientation) and does so from time to time. Theoretically the ISS could assume and hold any orientation around its X, Y, and Z axes. Typically ISS holds a constant orientation with respect to the Earth, essentially with the US lab pointed in the direction of travel and the axis perpendicular to the truss containing the solar arrays pointed at the center of Earth. Since the Sun’s position with respect to the ISS orbital plane and the angle of the Sun above
or below the orbit plane changes slightly each day, occasionally the direction of travel is reversed. When reversed, the US lab is trailing and the Russian segment pointed in the direction of
travel. This change of attitude is done for operational reasons such as keeping external equipment on the station cooler or warmer, by providing more shade or providing more exposure to direct sunlight. This can be done by changing which end of the station is in the direction of travel. Although I have not had chance to check the Mission Control timelines to see if this was the case on May 24 and May 25, it could account for the apparent change in the direction of travel perceived in the two photos.
Please let me know if there are further questions.

I have gone back and asked them if they would mind checking the mission control log.
Clear Skies,
Theo Ramakers