The following example sentence is quoted from Duden:
er fand den Ausgang der Sache bedauerlich, entmutigen jedoch ließ er sich nicht;
The word jedoch is labelled as an adverb in the dictionary; hence in the 2nd clause there are two words before the finite verb ließ which then occupies the 3rd position in the clause; does this violate the verb-second rule? How can we reconcile them?
The placement of jedoch in your example is indeed a little bit weird, as long as it is not enclosed in a pair of commas marking it an insertion into the sentence (as which I automatically read it, pauses included).
It would be no real problem (see your previous questions) if jedoch had been in first — or actually zeroth — position in that sentence. And it would also not be a problem if jedoch occupied a later position after the verb:
[…] entmutigen ließ er sich jedoch nicht.
Whatever the actual case is, while it is a violation of basic rules it is still okay if used for emphatic (or poetic) reasons. So I think you should just mentally mark it as an exception and move on.
