Hello Phillip,
Does the issue with the error 'corrupt file' persist? Regarding your problem with the jobs disappearing from job schedule, we suggest you to post another thread so that the different problem will be handled in it.
Regarding the Exchange mailbox backup issue, try stopping the anti virus scan and check if the error persists. Also from tools-options-backup, check if the tab 'enable single instance for backup' is enabled, if yes, disable that and then verify the results.
Revert with details if the issue persists.
Note : If we do not receive your reply within two business days, this post would be marked ‘assumed answered’ and would be moved to ‘answered questions’ pool.
Regards.