Thanks for that - I have done that already. In fact, everything is turned off apart from the minimal config that I need. I even did a full reset of my Draytek 2960 router.

Have you tried enabling (external) Syslog to Draytek's PC-based Syslog daemon?

There may be some diagnostic information written, prior to the crash.

Can I send the data to the Syslog on my Draytek 2960 ?

Not that I'm aware of

I solved all my network problems including the reboots by replacing the AP902s with Netgear box’s.

My AP902s became unreliable with a very slow web interface. I replaced them with AP903s. I also found that the rogue AP detection setting on the router was causing the WiFi to disconnect every 10 minutes, so I disabled that too.