Impossible to save assets after change in redirectors

One of our licensees pointed out this problem.

I've tried all the common redirector problems (write / read permission, multiple instances of the editor, renaming the assets, running the commandlet to fix the redirectors, etc) but still, impossible to fix this issue.

Open the linked project with in UE4.21

• Delete BP_Cube and replace the reference by BP_Sphere

• Try to Save