Rotary engines and their issues
 

I'm curious to learn about the most common issues of the various rotary engine models, I'm most curious about the 12a and 13b, but I'm open to learn about the others as well.
I'm aware of some, like the coolant seal groove failures on 86-2002 motors (which I unfortunately have experience with) or the irons warping on renesis motors, but I'm curious to see a compilation of all (or as close to all as possible) rotary engines for my reference, and anyone else's reference that might be comparing motors for a swap or something.

Thanks!