I wanted to update this thread. We applied build 9476 to three servers. After the update to 9476, two of the servers were stable. The server that we originally opened a ticket with support last year continued to experience the RAM issue.
We compared the servers and found that a large number of JSON files on the problematic server contained BOM characters, which I would assume came from migrating this server from Windows in order to see if the mem leak continued with Linux. The servers that were operating correctly did not have BOM characters in the JSON files. We corrected all affected JSON files, but this did not resolve the problem.
The issue was ultimately resolved by stopping the Index service, removing the IndexV2 folders for every user on the affected server, and then restarting the Index service. After doing this, the RAM leak stopped and the server has remained stable.
Hopefully this information helps anyone who is still experiencing this issue.