Router

I have a used HEQ5 Pro mount that no longer slews unless I operate it without any load on it. I decided to take it apart to see if I could locate the problem while also replacing the bearings. I’ve been following a couple of very helpful videos which have got me to the stage of taking apart the RA assembly. I have made it to the stage shown in the attached photo. Having loosened off the two backlash adjustment screws and the three set/grub screws in the black hub, I can’t unscrew the hub itself. The videos advise either tapping it with a screwdriver and hammer to jar it loose or applying a bit of torque with a set of slip joint pliers. I tried both methods, using considerable force with, in a moment of foolishness, a pipe wrench! Ach! I know how dumb that was, but so be it. The part never loosened at all. Can anyone suggest what I might have neglected to do (other than use more patience)? Or any other strategy for getting past this impasse?