Synchronizing a VDB takes too long in 7.4.2

Synchronizing a big VDB in version 7.4.2 (JBDS 4.1.1) takes 30 minutes versus 2 minutes in 7.1.1 (JBDS 4.1.0)

Investigating/debug noted 2 areas.
1) New UdfManager is not caching a FunctionLibrary and each SQL validation is creating a new instance. (needs a fix)
2) Synchronizing a VDB is hammering the ChecksumUtil.computeChecksum() during the VDB's resource build processing
3) PreviewManager is using a new Vdb() object to determine if "preview = true" and version #. However, it's heavy weight and currently the Vdb() is registering for events, but is not being Unregistered.