My bike is a Bianchi Virata from the early 1990's. Ultegra 8 speed groupset. I put new cables and a new chain on last year and ride 3 times/week in the spring, summer and fall. No issues whatsoever this season until 3 weeks ago. On a ride in mild rain I felt that the chain was not running smoothly then it snapped. So I had a new chain installed professionally (Performance Bike did the work). All was well. I had about 150 miles on the new chain with no issues and suddenly on a ride today it snapped. Shifting has been crisp. I have no idea what is going on and can't believe that relatively new chains would break just on their own.

Please let me know your thoughts.