Membership receipt shows data from wrong membership record

When a member renews their membership online, they receive an email receipt with details. That receipt contains the wrong membership data (Type, Start Date).

After investigating several examples, we've established that the erroneous data comes from a membership record whose membership ID is equal to the contribution ID of the renewal (which is associated with a different membership ID, the correct one).

This probably only manifests if the current serial ID of contributions is smaller than the current serial ID of memberships, so that there is an existing membership to pull bogus data from when a new contribution is created.

This looks similar to CRM-19094, which also was a case of doing something to a membership incorrectly by interpreting the contribution ID as a membership ID. That one was overwriting; this merely seems to be putting improper data in the receipts, but the membership records are correct within the system.