Zero clearance side seals round 2. (If you don't mind Barry)

[Slides]

I'm a bit sceptical about side seal vibration causing apex seal failure, the pressure differential across the long sides combined with deposits would mean a massive frictional force to overcome sliding back and forth in the side seal grooves, with a minuscule area at each end to provide motive force via gas pressures and very small distance for the seal to build up momentum.

Thanks for your continued input Barry.

Edit: couldn't let this go, and wanted to give a basic explanation for those playing at home.

The only way motion of a rotor could push/turn a side seal "backwards" (remembering that the oil seals have directional springs as well) was if you had entirely different e-shaft/seal/rotor design (leaving large dead zones on the sides of the rotors) which allowed the side/corner seals on one side of the rotor to be inside the tooth contact radius of the rotor gear. Not practical or desirable.

You can see this simply for yourself by drawing a rotor and stat gear and taking a radius from the point of tooth contact (the stationary point and centre of motion at any time) to anywhere on the rotor, only points lying inside the rotor gear can have a back/forth motion relative to the side plate (through an engine cycle). Even then it would only present a problem if the majority of an independently moving seal part was inside an arc of radius equal to teh gear radius from the tooth contact. That is you could have an engine design with circular oil control seals inside the rotor gear radius (on the off-gear side of the rotor) with the same directional spring design as ours without a problem.