Commentary
In this play at the very begining we are getting a theory on 4 types of bind.
Then we see thethe sholar who did a rebind and either is stepping forward in order to deliver a thrust, or it is the pries who pushes forward. In any case, the priest starts folding into a hanging guard (priest's special longpoint), but this attempt is defended by scholar's schiltslack in a similar way that we saw in frontal arms grab play.
Then we see a different branch of the play, where the priest succesfully gets from priest's special longpoint into back arms grab. Notice that the whole time, priest's special longpoint is not mentioned; maybe because the priest in fact doesn't fight from it. He just passes through in order to get into back arms grab situation. There is no mention that back arms grab should lead to a disarm, but it is a reasonable assumption.
Then we see the scholar who voluntarilly discarded his weapons in order to break free from the hold, and we see his grappling action. This in fact is an attempt to lean the priest back and then smash his back directly on the ground. This grappling technique has to be effective, otherwise the priest will get out of reach, and then it will be armed priest against unarmed scholar. In any case, this is the only way how scholar can fight from the back arms grab situation, if he doesn't want to just get disarmed.
In the last image, the priest is showing how he has defended the grappling of the scholar. He has raised his sword arm, turned around and pushed the scholar's arms away with his shield. This saved the priest from the hold, and naturally got him into sexta custodia, that is used in tha last image to threaten unarmed scholar.