I have the same error, same message on shutdown. Got it fixed with blocking using the method Elloquin linked (Watchdog didn't stop at shutdown - #40 by Elloquin). The only question is, why can’t this legacy watchdog just be left out? I was running Manjaro on my main machine until recently and my second machine (my girlfriend’s machine) is still running Manjaro KDE. There is no talk of watchdog more (was earlier there also once the case). If it really should be part of the kernel, they have it at least well removed.