Does the Postgres 9.4.9 update fix MultiXactId "does no longer exist" in addition to "has not been created yet" errors? Postgres 9.4.9 has a fix in it's release notes which reads (emphasis mine):

Prevent possible failure when vacuuming multixact IDs in an installation that has been pg_upgrade'd from pre-9.3 (Andrew Gierth, Álvaro Herrera)
The usual symptom of this bug is errors like &quot;MultiXactId NNN has not been created yet -- apparent wraparound&quot;.

I am currently chasing errors in PG 9.4.5 which read:
2019-10-19 15:37:17 EDT [13024]: [1-1] ERROR:  MultiXactId 1074790449 does no longer exist -- apparent wraparound

Does the above fix in PG 9.4.9 address the error I am getting?
I upgraded to PG 9.6.8. This particular environment is a legacy application that runs on an "appliance" style deployment so I'm forced into only updating to certain versions. 9.6.8 was the smallest increment I could take.

The initially appeared to have solved the MultiXactId xxxx does no longer exist problem with some simple queries. Subsequent queries to create indexes failed with the original error.