Quickly looked over your earlier posts about the mesh problems. To save you from burning more time on this, the only setup that has been reliable on NSS based 802.11s is forcing everything to stay 1 hop and putting the gateway node at the center.
I run a mix of MX4300 and MX5300 units. After a long stretch of trial and error, the result was always the same. Any time HWMP forms a multi hop path, it starts bouncing between routes and NSS has to relearn the path each time. That is where the packet loss and random slowdowns come from.
When every node has a clean direct link to the gateway, that behavior stops. Nodes still talk to each other directly when they need to. They just never route to each other through the gateway.
Setting mesh_ttl and mesh_element_ttl to 1, forces direct route
Experiment with the following:
edge nodes
option mesh_fwding '0'
option mesh_gate_announcements '0'
option mesh_hwmp_rootmode '0'
option mesh_ttl '1'
option mesh_element_ttl '1'
on your primary node
option mesh_fwding '1'
option mesh_gate_announcements '1'
option mesh_hwmp_rootmode '4'
option mesh_ttl '1'
option mesh_element_ttl '1'