Ian,
I presume the 'box has stiffened up in all gears - in which case, try removing the gear indicator (to make sure that is not pinching on the end of the gearchange shaft), and see if there is any improvement. If not, then remove the gearchange cover (6 Allen Screws) including the quadrant. Check that the quadrant slides freely on the key when slid back into place in the gearchange assembly. While the cover is off, check to see if the detent plunger has a small flat down one side (early plungers did not have this flat and have been known to hydraulically lock in the guide). Unfortunately , remedying this involves removing the 'box to undo the blanking plug that hides the end of the selector shaft (with the shaft out, the selectors can be moved to release the plunger).
Hope this helps,
Regards,
Eddie.
P.S. My Dragonfly did the same when first rebuilt - I checked it out and found nothing wrong, so put it back together and it's worked perfectly ever since (now done another 35,000 miles). I guess I must have just disturbed something!!
