Just guessing here but I think the ESD problem may be due to flowing liquid thru the guages. If you use an Imperial liquid converter at the refrigerant tank, that will break up the liquid and savae the sensors. I have not had a problem with my 2 sets but to be honest, I'm a part timer and don't use them every day.
Doug I was about to pull the trigger on a 550 after reading of improvements from Jim B.
Questions though How do we know if the units on the shelf in our area are the improved versions?
Also about the grounding strap. I saw no straps on display at AHR.
So the strap is for personal safty not the DMG
So I know it is not mandentory to use the grounding strap as far as warranty claims go?