The Sybase agent is running 'exec SYB_BACKUP...sp_who' and if that causes issues with Sybase, that has to be brought up with the Sybase vendor.
In the meantime, you can disable the backup server monitoring by the following:
- Go to Administration | Agents | Agent Status
- Edit the private properties of the Sybase Agent
- Click edit under the Availability Monitoring
- Uncheck the Collect checkbox for SybaseBackupServerStatus
- Save the changes and deactivate/activate the agent