How do I stop reminders from duplicating in Calendar app?

I'm on IOS 18 (previously 18.4, today upgraded to 18.5). I have a few monthly-repeated reminders, and I have the “scheduled reminders” function ON in Calendar.

The problem:

I keep finding the reminders duplicating themselves like zombies in Calendar on the day when it is scheduled. Usually when there's a scheduled reminder, there are 4 items (exactly the same) showing on the Calendar, 1 of which is the true one that I can deal with (edit, delete, link to Reminders, etc.), but the 3 others are all bugged ones that I can do nothing about.

Now, to feel better, I have to turn off that “scheduled reminders” function so that there are zero reminders shown in Calendar. But I still wish this issue could be solved so that I can turn it on again. I have tried the solution in this thread, but it didn't work (the author also mentioned the solution couldn't last long).

Hope someone could help, many thanks!

[Re-Titled by Moderator]

Original Title: Repeated reminders duplicate themselves in calendar