Hello gentlemen,
what you describe is here in Europe, where you do very often stumble into Sellier and Bellot brass as well as primers, very common reloaders experience. It works best to put S&B primers into S&B brass, or rework the primer pockets as the pockets as specified by S&B are a bit on the tight side! Actually the primers are not bad, maybe a bit "harder" than the US stuff, but not at all unreliable or inconsistent. However the brass is usually worn and torn after a lot less reloads than other brands. Seems to be a bit harder and therefore resizing is taking it's toll. Sometimes it helps a bit to turn the brass while trying to set the primer. At least it helps with my Dillon press.
Kindest regards from Germany
Lueftl