I found this, https://bugzilla.samba.org/show_bug.cgi?id=13647 , on the Samba bug tracker and the issue seems gone with 4.18 (which brings other issues so I'm back on 4.15).
** Bug watch added: Samba Bugzilla #13647 https://bugzilla.samba.org/show_bug.cgi?id=13647 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1811723 Title: Samba client freeze during write when using higher than vers=1.0 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-signed-hwe/+bug/1811723/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
