In the situation where you have FormatA and FormatB derived from FormatA.
In FormatA you create a mapping to model and in FormatB you run rebase process.
After rebase you can’t see a copy of mapping to a model in FormatB - it is lost.
The changes in the hotfix contain the code modifications that correctly rebase derived format. You need to install this package and repeat the rebase action for derived format.