I'd imagine you get surge marks along the perforation of your film if the rate at which developer is being replenished through the sprocket holes is higher than what's being replenished on the rest of the film surface. If you agitate too slowly this could happen, is the logical conclusion in my mind.
When I agitate my film, my standard pattern is to invert the tank a full 180 degrees, all while I twist the tank about a quarter turn. I do two or three of these inversions every interval depending on the size of the tank. My largest tank I can only manage two, and the smallest two I manage three in the period of ten seconds, including lightly shaking the tank and then rapping it firmly on the counter top twice at the end.
I have never had sprocket hole surge marks that way. But I have had it when I slow down agitation to much slower and gentler patterns.
I hope that helps.