Hello,
It seems like I'm doing this a lot these days, but you may want to contact Symantec support. For some reason the base images are having trouble of some kind (which is odd if you are selecting the "verify" option in your backup job) during creation.
They can likely gather logs/debugs (in your case they may ask for a copy of a corrupt base image, if possible) to dig futher into this issue.
Thanks.