Comment 25 for bug 1768627

@Mauro,

Thanks for checking, that's unfortunate that it's still happening.

To modify that file open it with an editor as root. For example:
sudo nano /lib/systemd/system/fwupd.service
or
sudo gedit /lib/systemd/system/fwupd.service

To view output from the journal:
journalctl -u fwupd.service

You can redirect that to a file like this:
journalctl -u fwupd.service > fwupd_journal.txt

Based on the output from that file I might have another recommendation to try to bump the TBT_NEW_DEVICE_TIMEOUT to something bigger (it's currently "2", try to set it to "3" instead).
This is in tree at plugins/thunderbolt-power/fu-plugin-thunderbolt-power.c

I'd like to see your journal output first though before you add that new variable in however.