I've posted an issue on GitHub and I have been advised to load RCBugFix. I have never used it and I do not know what is about.
What is it? How does it work?
It refers to a specific branch of the current project, named RCBugFix. It's basically the most up-to-date, bleeding edge version of Marlin that contains all of the most recent fixes (it is more up-to-date than RC). However, as it's so up-to-date, it's also not thoroughly tested and possibly quite unstable.
The latest Release Candidate lives in the "RC" branch. Bugs that we find in the current Release Candidate are patched in the "RCBugFix" branch, so during beta testing this is where you can always find the latest code on its way towards release.
Use with caution.