We have created a group in Crowd for developers who need to access Bamboo.
Adding a Principal in Crowd to that group has no effect in Bamboo
The Group Browser in Bamboo does no reflect the real situation in Crowd and shows the number of members to the group before adding new principals.

Because these principals also can not login to Bamboo we consider this as a blocking issue..
Rebooting Bamboo causes an update of its knowledges about the groups and allows our users to login