One of them is the contact muting options, which do not allow users to block notifications from a specific contact without actually choosing for how long this is supposed to happen.
In other words, if you want to mute a contact, you must choose between 8 hours, one week, and one year. What happens after one year? The contact is automatically unmuted, so you begin receiving notifications once again.
The Facebook-owned company is now working to resolve this thing with a dedicated “always” button that would be added in a future update.