Recently I wrote about the newly observed CBT bug in ESXi 6.x that, once again, could render your backups unusable. For the last two weeks only workarounds were available which could potentially lead to a extremely larger backup window and therefore making things not really better.
Fortunately VMware is used to fix these kind of problem quite fast these days and on 25th November they released an update to KB 2136854 with a hotfix included. VMware ESXi 6.0, Patch Release ESXi600-201511001 (2137545) will fix the new CBT bug and hopefully this is the last patch we have to wait for until CBT works as designed.
As also written in the notes to Patch 201511001 there is still a problem with HP ProLiant Gen9 servers that won't see their local disks after patching to ESXi 6 Update 1 and later. Keep this in mind when patching an older unaffected version of ESXi 6 to Update 1 or newer on a Gen9 server.
Veeam tested the patch against their backup product and it seemes that resetting CBT on all VMs is 100% mandatory to get the patch to work. So simply installing the patch is not enough, you HAVE TO reset CBT.