I have recently tried to use humaxrw (version 1.15) to copy some recordings from a 160GB drive taken from a Humax PVR 9150T to a local directory on my PC, which is running Xubuntu 22.04. I could successfully list all of the recordings by 'sudo humaxrw -l /dev/sdb'. If, however, I tried to copy a recording (say recording number 3) whose name contained a colon character, by 'sudo humaxrw -g 3 /dev/sdb', the copy failed giving the error message 'Invalid argument'. The same thing happened if I tried to back up all recordings to a local directory using 'sudo humaxrw -b /dev/sdb', which failed on the first recording whose name contained a colon.
It seems possible that humaxrw scans the names of recordings and rejects those containing a colon (and possibly other characters). This is, however, unnecessary, in Linux where all characters except null and slash are valid in filenames. Even in Windows, a better solution would be to use an escape character to encode characters like colon or simply to replace those characters by something like a caret (circumflex).
A workaround was to use the recovery mode by 'sudo humaxrw -r -g 3 /dev/sdb' but this was a bit clumsy as the names of the recordings were lost.