[alistairSH]

The sibling post to this covered much of it. As a previous RX-7 owner and racer, I can say the apex seals were prone to damage, especially if the engine was ever overheated. Much more so that overheating piston designs. The side seals didn't tend to cause as much problem.

And of course, with the Wankel, if any single seal fails, the entire engine needs to be torn down. With a piston engine, you can often pull the head to perform a valve job or re-ring a cylinder, without pull the main engine block. Not such a big deal on newer vehicles, but as cars aged, it tended to limit their value in the used car market.