Permission denied to update branch

In my repository, I have limited access to the 'develop' branch.
Pushes are limited to the Administrators and the Developers group.
The Administrators group has admin access to the repo, the 'Developer' group has write access.

This worked fine until recently.
Now users who are members of one or both groups cannot push to the develop branch.
They get the following:

Compressing objects: 100% (13/13), done.
Writing objects: 100% (16/16), 1.66 KiB | 0 bytes/s, done.
Total 16 (delta 7), reused 0 (delta 0)
remote: permission denied to update branch develop
To git@bitbucket.org:omroepntr/wetenschap-ntr-nl.git
! [remote rejected] develop -> develop (pre-receive hook declined)
error: failed to push some refs to 'git@bitbucket.org:omroepntr/wetenschap-ntr-nl.git'
Counting: command not found

I can push just fine. I am also in those groups, but am also included as 'admin' user on the repository.
If I remove the develop push limits, people can push, but obviously I want the restrictions to work. As far as I can see, all rights have been set properly (as indicated above).