Intake gasket failure

[Pandersen33]

Ive noticed now on 2 seperate engines that im having an issue of the outside of the heat riser holes tearing away from the intake gasket. Is this a common issue or should I be looking for a cause? Both planes are square and intakes were true. I used white grease all over the gasket. Im sure this could also be a reason i was having such an issue tuning the carbs if air can get into the intake from there?