Since the update, all my data is gone. Years worth of work. This is a major problem for me and my business. Suspect this is related to iCloud Drive.
Confirmed that this is on the mobile devices only. The website still has my tasks, thank god.
Now need to figure out what went wrong.
Deleting and re-installing the app worked.
P.S. Use the facility on their website to make a backup first.
MoneyMonk about Remember The Milk: To-Do List, v3.0.3