I am getting this error on a flow that has a subflow on retry

Finished in state Failed('Flow run encountered an exception. MissingResult: The result was not persisted and is no longer available.')

Will enabling result persistence on the subflow fix this?

From experience - yes. Though, I'm not sure which phase in the execution does this actually happen in (I.e. It would seem that a result is only needed when you have some step B that depends on step A and step A was successful so it's not being retried , while step B did fail which is why it's being retried .)