Pro Sites bug: Extend subscription "Permanent" isn't permanent

This morning about 10 of my pro sites that were extended permanently expired. I attempted to manually subscribe them permanently again and they wouldn't. As a work around I extended them the maximum I could manually, which was 36 months + 30 days.

How does the manually extend "Permanent" function work? Is it possible to make it indefinite? If not, can we make it + 10 years or something?