Why can't I extend Canvas Discussion due dates anymore?

[bmvaughn]

For the last 2 years, I have had the same late policy. All assignments are due AND available until their original due date. After the due date, students must submit a Late Work Google Form to get the assignment unlocked so they can resubmit it for credit with a late deduction. What I usually do is just add a new "assign to" box for that student with the OG due date and then extend the available date to their new deadline. Well, something about the new Open/Close comments setting that was added over the summer is making this not work anymore. On my end, it shows their assignment should be open, but on their end, there is no reply button and it still looks locked.

Other things I (and my district's digital learning team) have tried:

1) Changing the individual student's due date AND available date to a later date -- Same result as described above.
2) Change dates, press Open Comments -- Same result as described above.
3) Remove all due dates, save, close/open comments, re-enter the same due dates plus new ones, and then save again -- This actually worked, but the very next time someone needed the discussion open again it was stuck in the previous mode. I am not doing that every single time a student turns their work in late or is absent from class and needs it reopened.

The current solution has been to extend OG due dates AND available dates to the end of this grading cycle, but with this solution, all students can turn in the discussions whenever they want for whatever reason and I also have to manually mark them all missing or late dependent on their status. Why is there even an Open/Close Comment button if it seemingly doesn't work? Why was that added to Canvas randomly when you could always extend the dates however you wanted before? I do not have any screenshots, as I can't see this from the student side and I have already changed all the due dates.

I appreciate anyone's assistance with this issue. Thanks!