William is now the expert on the armrest maneuver.  In essence you will
drive out the pin that retains the arm.  Then you will tighten down the
"allen" head machine screws that hold the bracket to the seat frame.  If you
remove one at a time and apply a little  clear nail polish, blue loctite,
vibratite or similar light locking compound the naggly little monsters will
stay in better.

Do check to see that the weld that holds the tube part of the mount to the
flat plate isn't loose.  If so then have it welded before reinstallation.

When the bracket is secure drive in the pin again.

I use two "drifts" to manage the job or one drift and a 1/4" diam bolt to
hold the arm in position while you re-insert the pin.

If you're used to this sort of operation, only the drift is necessary.

So William, do you have that email wherein we discussed this?  If so do
post.

thx

pensioner