How does one identify the left-right adjustment screw on the lead door of a set of bifold doors?

(Sorry for lengthy exposition of background: I don’t really have a sense of which details are relevant and which can be safely omitted.)

I have a set of exterior bifold doors, on which I only ever use the lead door, effectively as a swing door; the remaining doors remain closed and with their locking mechanism engaged all the time.

Recently, when I attempt to close the lead door, the multipoint latch mechanism will not engage; when the door is in the closed position, I encounter insurmountable mechanical resistance on attempting to raise the handle to engage the mechanism (when the door is in the open position, the handle raises and lowers and the bolts extend and retract without difficulty).

A Google search turned up very-similarly-worded adjustment instructions from various door manufacturers (e.g. here), from which I learned that my next move should be to try adjusting a hex-key-operated screw on the lead door’s lower hinge in order to move the lead door from left to right. The first hex-key-operated screw I found was tiny (about 2mm diameter and 3mm long), and aligned in the hinge’s radial direction, about halfway along the length of the hinge. I proceeded to try adjusting this screw alternately anticlockwise and clockwise, through gradually increasing numbers of turns (i.e. 2.5 turns anticlockwise, then 5 turns clockwise, then 7.5 turns anticlockwise…). None of these operations improved the operation of the latch mechanism, and indeed it may have got slightly worse (in the sense that the insurmountable resistance arises earlier in the process of trying to raise the handle).

On my last set of anticlockwise turns, the screw reached the end of its travel and fell out of the hinge. After several attempts, I’ve been able to put it back in, and I’m reasonably sure I don’t have it cross-threaded (screw head looks parallel to local hinge surface on visual inspection, and I used the turn-backwards-a-little-while-under-axial-load-first trick); however, I now find that, long before the screw gets back to its original position, turning clockwise requires so much torque that I’m in serious danger of rounding the hexagonal socket on the screw head (indeed, I may have already filleted the corners of the hexagon somewhat).

After this, I noticed that there are actually some other hex-key-operated screws on the hinge: one of similar size to the one I’ve been adjusting, and also aligned in the hinge’s radial direction, but near the top of the hinge; and one larger one aligned in the hinge’s axial direction.

Hence, my main question is: how do I tell which screw I should have been turning to achieve the left-right adjustment of the door, please? My secondary question is: what can (or should) I do about the screw that I now can’t return to its original position?

Thanks very much.

As per @FreeMan’s suggestion, here are some photos to illustrate this:

The full set of bifold doors:

The lead door:

The hinge on which I attempted adjustment, viewed from the side:

The hinge on which I attempted adjustment, viewed from above: