That appear kind of odd to me, I would begin fixing
there.
But if you think there is possibly some
value in it, there is I believe an option in SER to send back literally
to what is printed in Via (as opposed to reversely sending to previous
hop's transport address). It is normally turned off, becasue Via content
is frequently useless (e.g., due to presence of NATs).
Would be thanks full if you did:)
... but if you really want to try, set reply_to_via=1.