When upgrading from certain versions of MariaDB, it is necessary that Innodb was shut down with slow shutdown previously, or the server will not start with the new mysqld.exe binary.

So far, this was ignored by mysql_upgrade_service.exe, but it needs to be there for reliable upgrade

mysqld should be stopped in the old version, started again (with old mysqld.exe) with --innodb-fast-shutdown=0, and stopped again, before attempting to start with the new version