Hi,
Meanwhile I found the solution in my case. I found out that not Microsoft is responsible for the impossibility to install this update, but Rollback Rx Pro. RBX is a way better alternative to the Windows Restore System, that don’t solve most of the more serious problems one can have with the OS. RBX (combined with a with Macrium Reflect cloned system on an external M2 SSD Drive for the worst cases) avoids very often the necessity to reinstall the system and saves a lot of time. But RBX don’t say that it must be disabled for some Windows updates and proposes only the option “Allow updates that cannot be rolled back” and “Turn off automatic Windows Update”. When I disabled RBX, the update could install. Thus, the honesty obliges me to correct my point of view about the actual updates, even if we encountered many problems with the major updates in last years, as also reported in the specialized computing press.
Hope, this last info can be useful for Rollback RX Pro users. This shows also that one the best solutions in the actual case is probably to search for interactions between third part software that have an influence on the system management and the Windows Update process. ;)