Just upgraded a customers 2860 to 3.7.4.2 - pretty minimalist config. ADSL and 2 wireless SSIDs, that's about it!

Sadly it is now rebooting every 6 hours or so, and I've had to revert..

Disappointing...

i am not sure if is disable by its default but try disable upnp and see if is better, you can also try an other modem code or load the VECTOR firmware (3.7.4.2 has 2 firmware releases), i have find the vector (not with a 2860) a better stable firmware than the STD

UPnP is disabled. I think vector is only for FTTC or am I wrong? It's on ADSL2+.

No doubt yet again another config corruption but the trouble is this will require another drive out to the site.

STD is for adsl2+ you are correct & also for FTTC
Vector is a special firmware for FTTC designed for vectoring lines , perhaps not available yet the vectoring ... but from my own experience with a 2760 (which has STD & VECTOR - same modem codes for both models) i have find it is working very good & for adsl2+
with the STD i had disconnections every 6-8 hrs and with the vector none
you can give a go (use the rst file & settings manual back from the begin or contact the support

if you are using adsl2+ you can leave the STD and just try an other filter