Thanks all for the help.
I _seem_ to have got everything working and stable (touch wood) but unfortunately not deliberately. I ended up having to replace my router and reconfigured all my wireless networks from scratch at the same time. Turned out to be a useful exercise since it seems to have resolved the LIFX issue too. But it did involve several changes all at once so not exactly a scientific method of resolution and appreciate that is super unhelpful for anyone else that has a similar issue and comes across this thread.
Just from comparing old configs and new configs, I think the most likely resolution was one or both of the following in the radio config:
- Turning up minimum unicast rate to 5.5 (I don't know why I had it lower to start with. Previous experimenting? Default config?)
- Turning off enhanced roaming
But I don't really at all know what I'm doing so may well have been something else. I base this guess off the error code 8 suggesting that the issue might be redirection to another AP. I did try separate IOT SSIDs for each of my WAPs at one stage and that didn't help.
From memory, I had previously tried toggling both of:
- Respond to ARP requests automatically on behalf of clients
- Unicast DHCP
But still had issues. Currently both are on and everything is working fine.
Other changes in the network rebuild include:
- Change EdgeRouter Lite to Cambium R201 - could well have been something odd in my ERL config.
- Getting rid of VLANs - I used these primarily for content control (adults, kids, IOT, guest) but am testing the RouterLimits option in the R201 (impressed so far). Could well have been something odd in my VLAN config, thought that seems less likely.
- Generally following the recommended base config unless I actually knew why I would want to change something.
Thanks again for the help.