I do not see any SERVFAIL here.
Note that SERVFAIL is a valid DNS reply as can be received from upstream servers. Respective replies are both common and expected every once in a while, but normally shouldn't reoccur when retrying a bit later, see also MS Teams gets no presence status for contacts - #6 by Bucking_Horn.
If that happens next time, check the OPT PSEUDOSECTION for RFC8914 EDE error codes, which may have more specific information as to why the SERVFAIL occured (e.g. it could be censored upstream).
You also may have to scrutinise unbound's log files in order to find out more.