For everyone else’s benefit, the issue was caused by this setting in the Advanced properties of the Project Manager:
The default path template looks like this, as @joeral mentioned:
It’s fine to edit that path, but it does cause issues if you start that path with a \. Removing that and using this path also allowed it to work: Reelname\{config}\AvidMediafiles\MXF\1 (though i’m not sure you really would want it that way).
We’re going to be using a similar structure for the custom output file-naming feature. In that case, we put some additional validation on the field to help give the user feedback as to what are valid tokens, etc. We may circle back to this in the near future to add some helpful hints here as well.