Some users of this forum have already encountered the problem that with the latest updates to Pro Tools, the Dolby Encoders and the external Atmos Renderer, there are differences in volume (e.g. compared to Nuendo). This is due to the fact that Dolby decided to make significant changes to the rendering process at the end of last year. (See the document linked below.) These changes caused problems that have now led Dolby to make a U-turn. In this context, a new Atmos Renderer update (v5.3) has been released, correcting the volume differences.
See THIS document for more information.
As you can see from the list, Nuendo’s internal renderer is not and has never been affected by this problem. (This has already been suspected elsewhere.)
Who would have thought that not being first would be a good thing? (Greetings to all Pro Tools users. 
)
The back and forth is quite annoying and problematic.