I'm inclined to agree with Kitz comments that if you have problems with these adapters there could well be other issues affecting the performance.
I don't know what the other issues that may be effecting the HG612 when the poweline adapter is plugged into the mains ?, the test last night was the powerline adapter plugged into the mains in 5 different locations around the house and the ethernet cable was not even connected to the unit.
My house is a bungalow and all mains wireing was replaced in 1996 and the circuit breaker board was updated in 2001.
I have had very stable VDSL BroadBand sync in the last couple of months since the removal of poweline adapters, now don't get me wrong I think it works well as a substitute for direct Lan to Lan cable but I can put my hand on my heart and say they cause more hassle on my VDSL BroadBand parameters and also my MutliBand Radio scanner is also affected by the PowerLine Adapters and it uses battery's not the mains
look at the two pics before and after the powerline adapters was connected ->
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