Cannot reproduce your problem with some of the NewBlue transitions in Sony Vegas Pro 13.0.453 (GPU on, Intel HD630 or Nvidia GTX1050). But if they actually are NB transitions you might read this comment. It don't take but a few seconds to test with the speed you are working through all of these suggestions.
@UncleJohny - Hi there! - No, it's not a transition type. NewBlueFx is the name of a company that makes many many types of FXs, I have a mass of 'em! Here's their Site:https://www.newbluefx.com/products/.