iOS app intermittently fails with “An SSL error has occurred” for some users — AWS backend with only an A record

I have an iOS app where most users can access the app normally, but a small number of users are unable to enter the app or load its content. For affected users, the iOS logs show errors such as: An SSL error has occurred, and a secure connection to the server cannot be established. or: A TLS error caused the secure connection to fail. The failure...