Mac mini Cluster via Thunderbolt bridges and static IPs to each mini, ping not stable

I have tried out several topologies to connect my 4 new Mac mini M4 pro with thunderbolt 4 cables (before going over to TB5). I want to work with exolabs (experimental cluster dealing with LLM). However, I get no stable setting, neither with Mesh topology (each Mac with each), neither with TB Hub. I have followed several strategies (setting IP and routing by hand). No chance. Sometimes I have all Thunderbolt connections working (green), but most of the ping connections , apart from a few, do not work (request timeout). I put thunderbolt on highest priority to avoid overlap with ethernet (or else). No chance. What can I try? There are some videos on a Mac Mini Cluster that work with such an approach.