tl;dr: either downgrade the kernel or switch to the LTS version.
]]>Error: Partition(s) (...) on /dev/sdb have been written, but we have been unable to inform the kernel of the change, probably because it/they are in use. As a result, the old partition(s) will remain in use. You should reboot now before making further changes.
The message won't go away even after rebooting several times and is present regardless which disk or usb I try to edit. Formatting usb completely doesn't seem to help at all.
I recently upgraded kernel. I will try to rollback it in the meanwhile. Any ideas on how could this be solved otherwise?
]]>