We recently upgraded to Moodle 3.8.3+ (Build: 20200626) and discovered a bug in the moodle code.
For some time, whenever we would copy courses, we would end up with teacher forum posts with a future created date. We have master courses which include standard teacher forum posts. When we created copies of these master courses, moodle would adjust all timestamps according to the difference between the time the master course was created and the start time of the new course. Because the standard teacher forum posts were created long after the master course was created, when we copied the master course to start, say, tomorrow, the teacher forum posts would all have created timestamps way in the future (e.g., September 2028).
This was never a problem (I don't think) until this upgrade. Students would occasionally write in about the odd timestamp, but moodle displayed the forum just fine. Now, when you click on a forum in which a parent post has a later created date than a child, all you see is the error: "Exception - Call to a member function get_time_created() on null". None of the posts are accessible.
I went into the db for one such forum, found the culprit post, and updated the created time to be 10 minutes before the earliest response to it. Once I made that one change, the whole forum is visible with all of its posts. I could do this manually in the db, but there are 2000 such discussions, and I'd rather not run a convoluted SQL query if I don't have to.
I searched around but was unable to find anyone with the same issue (my apologies if this is a known issue!). If this is a known issue, has it been fixed in a later version?