I recently purchased a 1960s Speed Graphic. It is in barely used condition and came with 6 barely used film holders. So much for the good news. My film back is so stiff that it makes getting the film holders in and out almost impossible- you need 3 hands to do it. They have to be forced so much that the far end of the film holders are getting marked, almost worn down. I’ve looked at the other holders that came with it that I haven’t used and they still look new, which tells me maybe I’m doing something wrong when I load and unload? Somehow the previous owner must not have had this issue. I’m stumped! Any thoughts would be appreciated.
Is the back adjustable?
Is there a way to lift the far end of the back as you slide (in my case force) the film holder into position?
Thanks!

Have you tried removing the Graflock spring back and lubricating the chrome arms where they fit into the casting? Use a thin oil. After that, you can work the arms until they feel looser.

The advice about lubricating the pivots of the arms is good, but I have also occasionally had trouble with the spring arms being bent and hampering the operation of the back. If you need to bend them back into shape, be careful not to put stress on the pivot hole. You may also find it helpful to simply move the arms back and forth a number of times to free up the bearing.

With a properly functioning back, you should be able to insert a film holder with one hand. Push the film holder against the two "ears" that protrude from the ground glass panel (that's what they're there for). This will open the back enough that you can push the film holder in, and from there it should slide to its final position without too much force. Remember that the Speed Graphic was intended to be used hand held, so that one had to be able to insert holders with a single hand.