Have you checked to see if the stanchions are straight bent legs can wear seals prematurely!
Also never fit new seals dry always lubricate with a littlte fork oil when assembling
Otherwise check the legs with a steel ruler to see if they have any surface blemishes which are not immediately visible, (hold them horizontal with a light behind if you can)
If they've been "cold" straightened in a press with "V" blocks they may have "ripples" which cant be seen with naked eye
Which is why "rolling" straight is the professional choice (when new is not an option due to availability or price)
Good luck
Em