Got a chance to look at the tray latches yesterday. There are three adjustment points. One at each end of the latch rod and a rod-length adjustment coupling near the middle of the rod. Unless the rod length coupling comes loose it would be unlikely to require any adjustment.
However, the position of the complete latch rod with respect to the ends affects the freedom with which the rod and the attached bent tabs can be rotated. The goal is to keep the right-angle bends in the latch rod away from the holes through which the rod passes.
To do that, the collars that are part of the bent tab assembly are positioned on the rod to keep the axial position correct and the radial position of the bent tabs located so that they will engage their respective notches in the framework to keep the tray from sliding to port or starboard.
The set screws in the collars are not very hard and can come loose. I had some button-head cap screws of better material and substituded them for the set screws. I had to grid some of the head off the outboard ones to clear the tray frame. I'll get some high-grade set screws for the permanent fix. The collars and screws are in the images.