All is working fine with WP version >= 5.6
So definetly this is the couple:
Use and keep ACF 5.9.3 with any WP version.
Update to ACF 5.9.4 only if you already updated your WP version to 5.6>
That’s all.
I can confirm that Rolling back to 5.9.3 solved the problem.
just wrote to the developer and get a reply from the team, They know the issue and that case is under investigation.
I’ll keep 5.9.3 until the next (5.9.5?) version.
Thanks to all!