"OSC" is shorthand for "On Screen Control". The value of the parameter (oscOptions) is not known to me. [It's ironic that when I first read this thread that I was tempted to tell you to dig into the XML of the project file... but I couldn't tell you what to look for.]
However, for a Motion Path behavior, as soon as you click on the behavior in the Layers List, the cursor should automatically go to Adjust Item. If you only select the object the Motion Path is connected to, then all you get is the regular cursor — you still see the path, but you cannot edit it.
Something within your project broke the 'link' from Motion Path to its object (it happens [not often, but...]). Usually when something like this happens to me, I just remove the "faulty" behavior and replace it with a "fresh" new copy. If that works, Save As a new version of the project (don't risk resaving over the "older" version). [I think you already do that for the most part.]
Try to remember the steps you take when constructing your projects — take breaks and save more frequently - it makes keeping track of changes you make... shorter...
If you figure out the oscOptions codes — please post them!