Hi Phil.
There has been a change of behavior between version 10.40 and 10.65. I noticed it using the API but it also manifests itself in the command line version. "flash" followed by "flash#" behaves differently.
egremont:Image-ExifTool-10.40 alan$ ./exiftool -G -a -flash -flash# ~/photographs/photo/2017/scuba.February/f200_4365.jpg -ver
10.40
[EXIF] Flash : On, Fired
[EXIF] Flash : 9
egremont:Image-ExifTool-10.40 alan$ exiftool -G -a -flash -flash# ~/photographs/photo/2017/scuba.February/f200_4365.jpg -ver
10.65
[EXIF] Flash : 9
[EXIF] Flash : 9
Probably related to this? (https://exiftool.org/forum/index.php/topic,8702.0.html)
Yes, there were problems in this area that had existed for a while, but are fixed now.
You should update to version 10.67
- Phil
Sorry, should have updated first.