I'm still encountering the issue in a new project. On a separate computer, I've created a new project folder with a fresh import of PlayMaker. I put Lane's "Get Mouse Position" (with "every frame" enabled) on a one-state FSM attached to an empty object. At runtime, the variable updates quickly two or three times, and then stops updating.
For good measure, I put a "Finish" event on the state and attached it to a second, empty, state (just to see if for some reason the action is marking itself as "finished" even though "every frame" is checked). The FSM never transitions to the second empty state, so the action still thinks it's running.