I believe, this error is about shadow copy components and not about SQL. So, please check for VSS related events on the SQL server, event logs. It appears to be an issue with VSS, as it is trying to use VSP and not VSS. Restarting server generally helps with VSS errors. Also, check the results of "vssadmin list writers" command on the target server. Do you see some writers that are unstable? Also, uninstall and reinstall remote agent without "Advanced Open File option". Try creating a new job too, as there could be a corrupt setting in the job forcing it to use VSP instead of VSS for shadow copy components.
Please mark it a solution, if this is useful.
Thanks