I have been made more tests.
It seems that with this version I have no problems exporting in jpeg or tiff (at least I could export some photos with no problem).
But when I use AVIF 12 bits it takes almost forever, more than ten minutes.
I was about to kill the process, but as I was writing this the process has ended.
So it was not hung but took more than ten minutes to finish.
When I try to visualize the creted file (11 MB with 12 bits 93% lossless compression for a 6000x4000 raw) I cannot see it in Photos under windows 10 (I have installed AV1 codec and other avifs are visualized OK).
May be it is a limitation of the codec in windows that does not support 12 bit or the kind of compression, I don’t know.