Same issue for me. I've tried different firmwares. Router mode. Access Point mode. Swapped units around. Had three units up and running, tried reducing to two. Moved them about. Connection can be OK...

I have a near identical problem. Jitter / Ping spikes when connected to the mesh network on my P9s. Ping is around 30ms, but can spike up to 800+ms, every few minutes or so. Makes online gaming...