Error building software stack


I have been trying to build the Morello software stack using the 1.3 release user-guide.rst and have not been able to get it to build.

The error I have been getting is:  

Submodule path 'llvm': checked out '47853ef78a113576a9f4e927fe46409a88f1c503'
Submodule path 'llvm-project': checked out '16fc6390465662de8e05f46313d61f697ede77f5'
fatal: Needed a single revision
Unable to find current origin/master revision in submodule path 'morello/llvm'
Checking out files: 100% (19217/19217), done.
Previous HEAD position was 47853ef7 Add binaries with a fix to lldb-server.
Switched to branch 'morello/baremetal-release-1.3'
Your branch is up-to-date with 'origin/morello/baremetal-release-1.3'.
Previous HEAD position was 16fc63904656 [Morello][lldb] Remove explicit dependency of Android source
Switched to branch 'morello/release-1.3'
Your branch is up-to-date with 'origin/morello/release-1.3'.
Fetching origin
fatal: A branch named 'morello/release' already exists.

Using the following command:
./build-scripts/ -p soc -f busybox build

Have I made a mistake somewhere or is there a problem with the repository?