Users unenrolled after 249 million days of inactivity

'evening, Everyone!

Some of our recently enrolled users (K12 school) disappeared from their courses with their submissions, gradings, etc. Driven by an intuition I run the cron script in a browser and found some weird lines in the log:

unenrolling user 2043 from course 823 as they have did not access course for at least 248832000 days

249 million days... It must be a bug.

User 2043 was enrolled 3 weeks ago into course 823 which is just 4 weeks old. Many of the un-enrolled users were active earlier today. Some users were un-enrolled from multiple courses.

Not all students were removed from the courses and not all courses are affected. We have a course where 24 of 25 students were removed, 1 single user remained. No idea what makes the difference between them. We also have a course untouched since 2013 and it has all the enrolments.

If 248832000 actually is not a number of days but a unix timestamp, then it's exactly 2880 days. Does it make any sense?

There are no error messages. We are behind a firewall and no external access available.