97K, V-Mach kit (standard apart from request to Mr Pope that the spring be half a coil shorter). Degreased the action when fitted the kit but didn't do any polishing.
GinB FT-1 stock
no shift. One or two occasions when stock bolt torque was suspected, but that could have originated between the shooter's ears.
Same action in Warren Edward walnut stock plus Bri Samson hook: more shift which does seem to be more sensitive to stock/action fit and bolt torque.
77K, full lazaglide, CS800 stock: Big shift due to stock bolt tension
My belief is that weird or unexplained zero shift in a springer (apart from sighting system - scope, mounts) is 70% shooter (clothing, hold, muscle tension, trigger technique), 25% stock fit to action, and 5% action (tuning, recoil).