Maybe I don't understand how subtasks are meant to repeat, maybe it's not clear or maybe it's a bug.
I setup a Weekly cleaning task with several subtasks. The weekly task has start and due dates. The subtasks have repeat with parent set and no start or due dates.
According to the help when I check off the parent task my subtasks should regenerate under the parent.
I'm not seeing this happen. What does happen is the parent gets regenerated with no subtasks.
I just tried a test and I got the same results as you did (parent task with no subtasks), but then I realized that I hadn't set the subtasks to repeat with parent. Then, after I did this and I completed the parent task (without touching the subtasks), it regenerated correctly along with the subtasks.
Have you tried this several times, always with the same result?
I must have been doing something wrong earlier. I was testing this with completed tasks and I think my parent lost it's repeat setting. Seems to be working now.
To be clear though, I can check off child tasks as I do them and then they'll regenerate when I check off the parent, right?