I've seen the same errors on a newly created VCSA 6.5b and even without Veeam activity I've seen those errors happening, and ultimately crashing vcsa every hour. I ended up doing a backup and restore of the appliance, and since that I've seen no errors anymore. Also, regardless what "strange" call Veeam would do, the write operation is done by vCenter against its own database, so if there's any chance that's the root cause, actually it feels to me that VMware should fix that problem. Veeam only engages official vSphere API.
EMEA Cloud Architect @ Veeam Software
Veeam VMCE #1