Issue with potfiles in v1.21

[unix-ninja]

This is intended behaviour. The outfile is really just another potfile, so if it's found in your potfile, it won't rewrite the result in the potfile. (even if it is a different pot)
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Just FYI, you should be able to use potfile-disable and --outfile together to get the result you want.
Alternately, you could remove your potfile before running your job as well.