Never let your speakers wash the dishes. (Sorry, could not resist. It's a matter of syntax.)
Seriously, it would help to know WHICH resistors are failing and whether in all 3 cases the failed resistors have a common function. For example, is it the phono load resistor for the R channel that is failing in all cases? You should be able to get that information from the guy who does your repairs. Also, in all cases, were you correct in visually identifying failed resistors; you tell us that this or that resistor looked like it was blown, but I wonder just what the problem(s) actually were. If a resistor blows, you usually think it was passing too much current, which increased the power handling required above the resistor rating (in Watts) and overloaded the resistor. Since the phono load resistor handles only a tiny current, many times the builder will use resistors with a very low power rating, which is easily exceeded. But not much can happen in that position in a phono circuit that would lead to that kind of failure. It's puzzling. But, if it's always the phono load resistor, that at least would narrow one's thinking.
Seriously, it would help to know WHICH resistors are failing and whether in all 3 cases the failed resistors have a common function. For example, is it the phono load resistor for the R channel that is failing in all cases? You should be able to get that information from the guy who does your repairs. Also, in all cases, were you correct in visually identifying failed resistors; you tell us that this or that resistor looked like it was blown, but I wonder just what the problem(s) actually were. If a resistor blows, you usually think it was passing too much current, which increased the power handling required above the resistor rating (in Watts) and overloaded the resistor. Since the phono load resistor handles only a tiny current, many times the builder will use resistors with a very low power rating, which is easily exceeded. But not much can happen in that position in a phono circuit that would lead to that kind of failure. It's puzzling. But, if it's always the phono load resistor, that at least would narrow one's thinking.