A couple of weeks ago I found our internet was slow / non-existent in the early evening. Re booting the router seemed to resolve it, but after several consecutive days I finally twigged it only happened when the sun got round to the west, and then shined in through the utility room window. The router was here, sitting in full view of said heat source, and subsequently keeled over... Re-positioning and putting some white card in between the two solved this problem!