Hi, Can you please clarify that if this issue is present with the Dolby Atmos Mastering Suite or the Dolby Atmos Production Suite. And that this is running on an HDX system. If I understand correctly you are seeing variable latency with any custom re-render using groups vs full mix. Is that correct?
Please also let us know what version of the Renderer you are using.
I'll need to get some feedback and do some tests. With the Mastering Suite Renderer running on an RMU using a 2pop or plop is a workaround.
Sorry for the delay in getting back to you.
Delay compensation in Pro Tools is on the physical output. The inputs to the renderer come via the send plugins which are on aux tracks so automatic delay compensation for plugins is not applied. When you put reverb on tracks that feed the Production Suite via the send plugin on aux tracks the audio needs to be shifted earlier to maintain sync. In Pro Tools if you go to View/Mix Window Views/Delay Compensation you can see the amount of the shift (in samples) that will need to be applied.
When using the RMU with physical outputs you don't need to shift anything earlier as the plugin delay is compensated for via the amount in the Delay Compensation view. However the RMU itself has a fixed latency of 44ms so you will need to shift any re-renders that you record back into Pro Tools once the recording is complete. Using a 2pip/plop is the best way to do this.
Hope this helps.