PPPoE Dial On Demand Or Always On Problem

[Spandex]

Set up my router on PPPoE and bypassed having the bt router plugged in completely and it was automatically set to dial on demand, so i tried switching it to always on, but if i do this about an hour later the internet cuts off on the router for about a minute and then when it comes back on we have internet but now at 1/10th of the speed, 930mbps down to 93mbps, always guaranteed 1/10 exactly, have no idea why but it has done it 3 times now without fail by changing from dial on demand to always on.