Usually we assign permissions to a group, not to the user itself. When you say you assign user permissions you basically assign the user's "default group" I think.
In general when you start crossing groups it is possible that you experience inconsistencies, due to the way the permissions model is designed. I would say stick all the permissions you need to perform what you need from start to finish rather than trying to combine groups that way. The reason it is that way is in case you want to exclude certain permissions from a user, but it is not always intuitive.
-- Filippos Chalvatzoglou Server Automation & BSA Essentials Support HP Software
If you find that this or any post resolves your issue, please be sure to mark it as an accepted solution.