Can't understant weird behaviour in file editing collaboration in Nextcloud


I can’ understant the way file editing collaboration works in Nextcloud.

Let me explain:
I created a basic text file, on a shared folder and I wrote a few lines on it. Then, another user edits the file, adds a few more lines to it. Then, just as an example, I add more lines. The idea is to explain at least two users changed the file.

The file has the versions and the comments correct, as expected, but on the file details/activity one of us can see the other changed the file, but the other can’t (sometimes is one, sometimes is the other, both of us are admins).

This behaviour is weird, seams like a bug. Am I understanding something wrong?

I’m using Nextcloud 12.0.3 on Docker 17.09-ce, from Official Docker Hub Nextcloud image.

Thanks a lot for your help.
Best regards,
Luis Nabais