10 ohm R's going high - problem.

[ppppenguin]

This is pretty extreme. Vishay resistors are excellent quality. About the only thing that might kill them apart from gross sustained overload is pulsed overload. That could blow them open circuit, as with any film resistor. I don't understand how they might go low.

Why do you need 1% parts? Valves just aren't that accurately matched or specified.

For ultimate bomb proofing use small wirewounds.