Yeah it's an estat thing. TBH I don't recall noticing it on my ESP-95X, but I demoed an Audeze CRBN at CanJam and literally thought the headphone might be broken. Wasn't an occasional if-I-move-my-head-just-so sorta thing, it was as ever-present as the swish of a swishy jacket.

BTW, I graphed the ESP with stock and those Vesper pads, the pads do good stuff! https://squig.link/headphones/?share=Super_OE_Target,Koss_ESP-95X,Koss_ESP-95X_(Vesper)