Also, post your DSL line stats immediately after a reset, and in the minutes leading up to the four hour window.
Additionally, can you borrow or buy another modem that is a different brand to the ones you have tried?
net888: Its every 4 hours from reset. On the dot. This morning it was reset at 5.30 am. Then again 9.30an. Oh guess what? Also being reset rught now too1.3o!!!
Involuntary autocorrect in operation on mobile device. Apologies in advance.