Invalid branch name but branch created (BB-10834)

Hi,

Some times when I try to create a branch in bitbucket i have an error "Invalid branch name".

But the branch have been created and if I click again the button I have the message "A branch with this name already exists"

This issue happened on every repos but it's not every time I try to create a branch.
It just happened on the repo ccmbenchmark/testrepo when trying to create the branch "preprod" from the master.

Thanks.