I bought a set of these just for spares: https://tteglobal.com/audi/rs4/b5-2....nsors-egt-pair
I replaced mine with new OEM Audi parts around 10yrs ago as preventative Mx when I had the engine out for Miltek downpipes. I was assuming the newer Audi parts wouldn't have the circuit board issues that the originals had on many cars but I was wrong. A few years ago I had the issue with one of mine. It took me two attempts but I repaired mine, couldn't visually see the bad solder but just redid the connection shown in the post above and on the second time around it worked. So now I'll have the TTE set as spares as I'd prefer to not code out my EGT's as I am running higher boost so most likely higher temps.