RDS Instace Edit Bug

Dear Customer,

Thanks for reaching out to AWS via re:Post.

Regarding your query, we have seen such issues when the engine version is no longer supported or deprecated - Once a version has been deprecated, there is a "slow phase-out process" which takes place and this typically affects the Management Console first.

As a workaround, I can suggest to try the modification via CLI. For further de-bugging I would also recommend you to reach out to AWS Premium Support with a case so that a deep dive is done

Thanks