Duplicate notifications can be caused by duplicate tasks rather than multiple devices. Could you use Search to check that there's only one instance of the task you're getting the reminder for?
If everything looks fine there, please send us the logs from MLO on your Android device so we can take a closer look:
Settings > Troubleshooting > Send logs to
sup...@mylifeorganized.netUsing MLO on several devices shouldn’t cause this, so no need to uninstall anything yet.