The issue is that the metadata files are not being updated by Lifecycle Manager. This can happen when somebody replaced the metadata.zip file with an older version and then attempts to sync updates using UMDS/VUM/vLCM. This information is available in /storage/updatemgr/patch-store/hostupdate/vmw folder by logging into the vCenter.
On expanding the depot folder under consideration, it can be observed that the release timestamp in both the metadata files (the one being replaced and the one it is being replaced with) under consideration are the same and as a result sync updates is not updating the content.