I can't answer what is happening here. But can you obtain more information using SysRq-t and SysRq-m as described at https://akari.osdn.jp/capturing-kernel-messages.html#Tips5 ?
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1762450 Title: [18.04] writing on thumb drives causes hang for write op, shutdown and 'sync' command To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1762450/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
