The issue occurs on controllers where the right-trigger (or any trigger for that matter) has been used enough that it has lost sensitivity. Thus, where a relatively new controller would easily fully register when pushed down at normal strength, a used controller may only register 80% and thus never kick off the input event.
For the time being, players who encounter the issue should switch to another controller or, if you're willing, press down the trigger as hard as you can. It seems to get more responsive after that. A permanent fix will be included in the next patch!