My BMW has been using 205/50ZR17 Continental ExtremeContact DWS tires for the last 5 years. Over those 5 years I have had to replace 10 of them due to blisters (usually on the inner sidewall), cuts or blowouts all but one caused by potholes. And twice two at a time. Potholes are epic in Pennsylvania due to dramatic freeze/thaw cycles and poor maintenance budgets. All of the inner blisters were discovered at annual PA State Inspections and came as a complete surprise. I have never had any of these problems in 55 years of driving before owning a car with 50 profile tires. You are driving on 40 profile tires, yikes.
I’m going with POTHOLES!
BTW: Continental has paid for the tires (4 of them) when they were less than 1 year old.