2 hard drives in RAID 1, why do new files disappear and old ones appear?

Question

RAID

There are 2 screws combined in raid1, a problem has recently appeared, I will explain with an example:
Let's say there is a "Document.doc" file from 03/01/2019, replace it with a new file (or delete and copy a new one there) with the same name, but from 05/15 .2019, open and check that the file is new. After some time (maybe a couple of hours, maybe a day, two ...) we go in, look, and there is an old file from 03/01/2019.
What is the problem, why is this happening and how to deal with it? Has anyone come across?