Okay I'll offer up this fwiw on what my OE shocks were doing before I coughed up the $700.00 +
Over undulating road surfaces, not potholes or sharp bumps, just gentle waves in the road surface at speed the car would wallow & porpose. It was a gradual type of thing. Like in tour it would be pretty bad, so switch up to sport & it went away. Then it got to the point that even in sport it would happen. Try perf mode and it went away. That's when I figured there must be something wearing/worn out?
I don't have C/O's, but if you send the shocks to Bilstein or DRM & tell them you're going to C/O's they will put the grooves in the rods when rebuilding the shocks.
Tom