I've tested this on Ubiquiti UniFi and TP-Link 842N V3, both run on ar71xx - the moment I launch a second instance of coova-chilli (attached to a separate wireless interface/tunnel), LEDE just crashes instantly.
There is nothing useful in the logs or in chilli's debug output. I tried disabling all hotplug hooks - didn't help.
Tested this on other architectures and it works just fine so it's either related to UniFi and TP-Link or ar71xx tree.
Anybody ever faced something similar? I couldn't find any info online