So I opened the backup copy jobs to the full 24 hours and the interval is set to run every day at 8am. Still have the same issue. I was thinking of running it once a week with a 7 day interval, but if the full backup isn't complete, it will just pick up the previous incremental, or if another incremental has occurred it would just pickup that incremental, so its a bit too risky.
I only care about copying the full backup every week, but it doesn't seem to be an option in backup copy jobs and it would be a great option (and one that should be pretty easy to implement). I could then run 7 day intervals and just do the copies during the week.
So I'm thinking the seeding could be part of my issue. When I look at the files I'm seeing a 33.5 MB monthly backup, for a server that is 13 TB. I'm also working on splitting that server into two smaller servers, but would still like to understand the root cause of my issue.