Engine is sitting on garage floor on its bottom and mount leg.

I un-threaded the head bolts to the point (~1" out) where their grip threads should now be disengaged from the block. However, 4 or 5 of the middle head bolts are still very stiff & tight and will not disengage for withdrawal. Side load on the head should be taken by the dowel pins and by the strap attached to the overhead hoist, so side load should not be binding on these bolts.

What am I doing wrong? Why won't these bolts just get looser and come out like the others did? Nothing of this sort happened with other M30 head removals. At the end of a long day, I thought it best to get some objective advice before monkeying further.