Old muscle injuries, in my case, with a tendency for those muscles to get extremely tight if I'm not careful with my stretching and fitness. When I've failed to keep the hip flexors, groin and glute muscles sufficiently stretched and capable, then no matter what I do with the CX-5 seats (or another car's seats for that matter) eliminates the aches. Something to consider, above and beyond whatever seat or position changes you do.
Position-wise, I also find that with my power/adjustable driver's seat if I tilt it rearward but then move the back/upright portion to where it should be, I can dramatically reduce strain on my back.
Have long been mulling the idea of having a bracket made for a Recaro Ergomed seat, for my 2016.5 CX-5. That'd be perfect, with all the adjustability, firmness and leg support that one could imagine. But haven't found the CX-5 seat to be insufficient, yet.