Under some circumstances .map.tmp files can accumulate to the root dir / of your (c)ESXi server. It is unlikely that they can cause harm as they are generally rather small. This issue exists since 126.96.36.199 maybe before. We'll fix it in 188.8.131.52
We are about to release the fix for this. Until you can download and install 184.108.40.206 VMs with CBT enabled should be backed up in its own job and let non CBT VMs run in a different one. This issue is just a consequence of the mix of the two kind of backups not playing well.
We have given this bug the maximum priority and will be solved in short.