When I complete a repeating task with subtasks, then complete one of the subtasks, the subtasks seem to be duplicated, at least visually but somehow inter-connectedly, because when I complete one subtask its copies also complete.
E.g.
☐ Task X repeat daily, due today
☐ subtask A
☐ subtask B
Complete Task X, and I have a new copy due tomorrow, but when I complete subtask A, I get:
☐ Task X due tomorrow
✓ subtask A
☐ subtask B
✓ subtask A
☐ subtask B
Opening it up in Reminders Note section, it looks like the items actually did duplicate.