I’m trying to create a new branch on github repo. I have local branche dunfell/rsbc and remote branch dunfell/rsbc/release

p@CND:~/workspace/build-scripts$ git push -f origin dunfell/rsbc 
Total 0 (delta 0), reused 0 (delta 0), pack-reused 0
To github.com:RSST/build-scripts.git
 ! [remote rejected] dunfell/rsbc -> dunfell/rsbc (cannot lock ref 'refs/heads/dunfell/rsbc': 'refs/heads/dunfell/rsbc/release' exists; cannot create 'refs/heads/dunfell/rsbc')
error: failed to push some refs to 'github.com:RSST/build-scripts.git'

Why does the existence of release branch lock up the creation of a different branch?
How do I fix this?