The Veeam Backup Service uses a system of timed leases as part of monitoring the many processes it manages. Usually this error involves a five minute lease for the VeeamAgent processes (Data Movers). When the Veeam Backup Service is operating normally, this lease is continually renewed. If the lease expires, the associated process is shut down.
Typically the lease will expire either because the system time has changed by several minutes, or because a problem communicating with the Veeam Backup Configuration Database has prevented the Veeam Backup Service from renewing the lease.