The strangest thing happened while upgrading to Joomla 4.3.4.
When starting the update, time forced me logged off.
After relogging in, the backup started as what should be normal before upgrading Joomla.
However, the backing looped over and over again.
Stoppping was possible, giving it a HALT situation.
I forced the site to restore from the provider's backup not any Akeeba backuo.
I started the update process once more, no problems since.
But I thought, I let you know what happened.