Absolutely not true and that is a very dangerous and misleading assumption. As an example, the datasheet for a Panasonic ERJ Series thick film resistors clearly states that the maximum working voltage is either your equation above or "the Limiting Element voltage stated in the specification table - WHICHEVER IS LESS".

Datasheet here: https://www.farnell.com/datasheets/2883945.pdf

For the 1812 size package in this range the limiting element voltage is 200V, so the resistor should never be used at a voltage higher than that. Increased voltage rating should be achieved by either a correctly rated resistor (special high voltage SMD resistors are available but they are usually bigger than 1812) or a number of resistors in series.

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Yogesh: thanks man. have a blessed day

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Tayo: I think it is a user issue since the cable was abused because it was bent in many areas. the cable was replace with a high quality one and so far no complaint. have a blessed day

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Jim: yes I am becoming a dentist dealing with cavity...LOL. have a blessed day

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Parasuraman: thanks man. LOL yes indeed. poor customers though. have a blessed day

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Imoudu: that is why I replaced the whole defected cable with a high standard one and so far no complaint. have a blessed day

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PS2: Although more high ohmic resistors in series would be advisable for HV safety we could better use two 5Mega-ohm 1% resistors in serie instead. But in this case those seem not to exist. Why for my new to build project, this 1KV HV grafical curve tracer tester, See here =>
https://www.printables.com/model/347158-high-voltage-1000v-isolation-tester-1kv-curve-trac ,
I only use one 1812 10Mega-ohm resistor instead. Which was the biggest smd resistor I could find. This DIY project is like the fantastic DY294 high voltage component tester but now with a graphical 1.77 inch TFT lcd, that tests semiconductors and other components safely upto about 1000V and shows the break-down voltage of diodes, transistors, vdr's, etc. in a real curve. With a safe 0,45 mA max limited short current on its HV output.

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