DNS Only Replication to 4 name servers takes extraordinary long holding up the WHM User Interface, > 75 seconds

We have a few primary WHM/cPanel servers that are integrated with four independent WHM DNS Only Servers spread on three continents. When we do anything in the DNS it takes extraordinary long, around 75 seconds for any change, e.g. an addition, an update, a deletion. The infrastructure and all servers are 100% performant, so I'm quite sure the problem is that the source server communicates with the name server hierarchy and holds up the WHM User Interface until the DNS changes are completed. I made some DNS changes to a competitor's WHM and their UI immediately came back so I'm almost certain that WHM has a background queue that for some odd reason isn't activated on our servers. Any tips?