I do save the custom roles and venue preset on both sides after correcting it, but it makes no difference to this issue.
Randomly some of the roles (5-15 of them) are lost in the active venue (right) side and I have to drag them back over from the saved preset (left) side. I always make sure the roles are saved on the active preset on the right and I frequently save that back to the custom preset on the left (including overwriting all roles) after correcting the data loss. Note the order on the channel list main venue page (hence the active preset side as well) is never loaded the same way twice and thus never matches the saved custom preset role order on left of preset page.
I have also tried dragging the whole venue preset including roles from the left to the right. Which incidentally, if I clear the right side, never brings over my custom roles. It looks like they are all coming over but when I drop them, none are transferred. And I have to drag them one by one because the order doesnt match.
This happens about one in every 3 days or so, or sometimes consecutive days. The particular roles lost do change, but there are some that seem to be consistently lost, when it happens that is. If I save my project in nuendo as a template and use that template in a new song, most of the roles in the active side are lost due to the order mismatch.
Weirdly I notice as Nuendo loads the project, most times (but not always), it will first bring up all the roles correctly during the project load, but then towards the end of the loading process I watch the venue get reset and rebuilt/repopulated, and that's when the roles are lost. So, somewhere in Nuendo it remembers the icon positions, but it borks and reloads incorrectly.
Also, Nuendo never loads the tracks, that have MIR loaded as the VST panner, in the same order. So each time the project loads the active preset (right side) and main venue page list order is different to the order of the saved preset (left side).
So if MIR is relying on matching the roles via the order of the list, its a flawed approach. Surely it must be using the name of the role. For me this always equals the name of the Nuendo track, no matter how much I have tried to name it differently in MIR, it reverts to the name of the Nuendo track, which I make sure is a unique name.
I'm using Nuendo 13.0.41 on Windows 11 latest and MIR latest. MIR instantiated as a VST panner on a large disabled 3300 track midi only template with remote VEPro servers. The very first channel in nuendo, up the top of the split channel view, is my "master" MIR channel (as has been suggested by VSL) as an insert with the master bus width (7.1). I earlier had this master channel as a VST panner but the issue was happening then as well. Changing it to an insert seemed to improve the issue but not solve it.