ReadyNAS OS 6.5.0 Archive Bit backup to Windows share not working.

I'm having an issue getting Archive Bit backup to work. Timestamp backup works perfectly to the same Windows share, but I read that Archive Bit was the recommended mode so I wanted to swap the job over to it. I did just that and now the backup will not complete, and the source/destination field on the job says 'share: Source -> No longer available'. However, when I edit the settings and test the connection to the destination it shows no errors. When the job actually runs it fails with 'destination cannot be accessed'

I thought this might have been because the job started as timestamp then was changed, so I tried creating a new job and realized Achive Bit isn't even an option for new jobs, you can only create a job as timestamp then switch it over (and it has the same 'No longer available' message on the destination). Is this intended or some kind of bug with 6.5.0?