Have attempted to duplicate your issue multiple times and with multiple users. I can not seam to duplicate. I believe your issue is related to misconfiguration of your docman permissions. Please see the following used configuration (DOCman > Configuration > Permissions).
Upload = Custom Usergroup (custom group here only)
Approve = Publisher (don't set your custom group to be approver)
Publish = Publisher (don't set your custom group to be publisher)
Maintain = Publisher (don't set your custom group to be maintainer)
Override Maintain = Uncheck BOTH (prevents user from changing maintainers)
Allow individual user permissions = No (is slow otherwise)
We will be closing ticket as non-issue as can not find any bug.