3.5.1
There are loads of users that appear to have had the lastaccess time for all their courses set to the same value. It's clearly intermittent - some did this today. Some did it a month ago and seem to have been recording sensible values since.
Yeh - I know it's not the best report but I was posting on the off chance somebody had seen this before.
My initial thought was some plugin calling require_login() when it shouldn't but I haven't spotted anything.
I'm struggling to see anything that connects the users but I'm still looking.
Here's a random example (timestamp found from searching for multiple examples of same stamp). This stamp applies to lots of courses for only two users.
select * from mdl_user_lastaccess where timeaccess=1543612400 order by userid;
+---------+--------+----------+------------+
| id | userid | courseid | timeaccess |
+---------+--------+----------+------------+
| 1837612 | 102053 | 1319 | 1543612400 |
| 1506024 | 102053 | 11795 | 1543612400 |
| 1506026 | 102053 | 1244 | 1543612400 |
| 1506027 | 102053 | 1242 | 1543612400 |
| 1506028 | 102053 | 1260 | 1543612400 |
| 1506029 | 102053 | 1239 | 1543612400 |
| 1506030 | 102053 | 1257 | 1543612400 |
| 1506031 | 102053 | 1235 | 1543612400 |
| 1859274 | 102053 | 15308 | 1543612400 |
| 1506025 | 102053 | 11797 | 1543612400 |
| 1837611 | 102053 | 14422 | 1543612400 |
| 1837610 | 102053 | 14656 | 1543612400 |
| 1813951 | 102053 | 14445 | 1543612400 |
| 1775727 | 102053 | 14412 | 1543612400 |
| 1775742 | 102053 | 14416 | 1543612400 |
| 1813949 | 102053 | 14411 | 1543612400 |
| 1798526 | 102053 | 14414 | 1543612400 |
| 1800800 | 102053 | 14413 | 1543612400 |
| 1465955 | 102053 | 11782 | 1543612400 |
| 1380032 | 102053 | 11790 | 1543612400 |
| 1389793 | 102053 | 11794 | 1543612400 |
| 1883804 | 102053 | 13038 | 1543612400 |
| 1375617 | 102053 | 5289 | 1543612400 |
| 1375584 | 102053 | 11783 | 1543612400 |
| 1367238 | 102053 | 11799 | 1543612400 |
| 1360600 | 102053 | 11798 | 1543612400 |
| 1873536 | 102053 | 13080 | 1543612400 |
| 1465958 | 102053 | 1237 | 1543612400 |
| 1465964 | 102053 | 1231 | 1543612400 |
| 1506019 | 102053 | 11774 | 1543612400 |
| 1506020 | 102053 | 11775 | 1543612400 |
| 1506021 | 102053 | 11784 | 1543612400 |
| 1506023 | 102053 | 11788 | 1543612400 |
| 1506022 | 102053 | 11785 | 1543612400 |
| 1889898 | 102188 | 11500 | 1543612400 |
| 1883795 | 102188 | 13038 | 1543612400 |
| 1842649 | 102188 | 5728 | 1543612400 |
| 1858479 | 102188 | 13080 | 1543612400 |
| 1858481 | 102188 | 15308 | 1543612400 |
| 1659000 | 102188 | 1944 | 1543612400 |
| 1806576 | 102188 | 4326 | 1543612400 |
| 1782718 | 102188 | 4608 | 1543612400 |
| 1666640 | 102188 | 4313 | 1543612400 |
| 1666639 | 102188 | 4324 | 1543612400 |
| 1666638 | 102188 | 4592 | 1543612400 |
| 1666637 | 102188 | 4593 | 1543612400 |
| 1666635 | 102188 | 2860 | 1543612400 |
| 1666634 | 102188 | 2858 | 1543612400 |
| 1666633 | 102188 | 11501 | 1543612400 |
| 1333989 | 102188 | 3043 | 1543612400 |
| 1443260 | 102188 | 6150 | 1543612400 |
| 1394243 | 102188 | 2883 | 1543612400 |
| 1394242 | 102188 | 3322 | 1543612400 |
| 1340092 | 102188 | 10102 | 1543612400 |
+---------+--------+----------+------------+