the same issue is in the web browser.
I’ve found that it is not that tasks as milestones do not appear - it is sub tasks as milestones. But since all of my milestones in one of my projects are subtasks then it appeared that none of them would come up in the overview page.
This is expected behavior, so I’ve moved this thread out of Report a Bug.
As you found out, subtasks are not considered to be members of the project like top-level tasks.
You can rectify this by showing the milestone subtask in the task detail pane, typing Tab+P, and adding the subtask into the project. This will cause the milestone to appear in the Overview, but also have the side effect of making the subtask a top-level task. A common workaround is to add a collapsed Hidden Subtasks sections tucked away at the bottom of the tasks list and make the project membership be directly to that section, out of view.