The option --ask-tracknum has no effect at all. The option --force doesnt't force the asking of the tracknumber.
Seeing the source code, the flag is well handled at the configuration level, but there is no code associated with it.
The proposed .diff patch correct the problem: now the tracknumber is searched in the existing tags of the file, and if --ask-tracknum is set, question is asked to enter/modifiy the tracknumber.
As I'm not a perl guru, this patch is only modified cut and paste...
Proposed Diff file