Honest question, as I've just recently started fiddling with Meshtastic: could it be that the mesh is not set up correctly for a dense environment? (e.g. using LongFast rather than MediumFast, or not having more nodes configured as client_mute?) I know the conditions may be wildly different, but just as an example, the guy in this video says he saw no big issues on a hamvention with 300+ nodes: https://www.youtube.com/watch?v=aBfHAPpjtk4

We are not seeing a correlation between channel saturation and/or alien non-related stations.

IMHO MT has a fundamental algorithmic flaw when it comes to dealing with very unreliable and lossy links.