If i want to open a fits image with version 1.2.5 processed by siril 1.2.4 i get an error message, that there is no ffopen file present. If i process the same stack with 1.2.5 there is no problem.
I have a win 11 system and use the portable siril since i have no space on drive C:.
This is a known problem that has nothing to do with FITS but with the FITS path name, if it contains special characters. This problem will be corrected shortly.