Originally Posted by Kf4mnc
To my hands it feels like a indentation on the back side and a bulge on the outside.
That's where I'm having a problem. In my experience, it should about feel the same on both sidewalls, if it's undulation. It's possible that the cord ply are broke at the same spot where there is undulation........which is why you have a bulge on one sidewall and an indentation on the opposite.
To make sure we are clear on where you should check the opposite sidewall at, I made this pic. The red oval is the assumed undulation. The arrows point to where you should check on both sidewalls for matching characteristics.