So, me and my friends are playing on a Realm server, owned by one of my friends (pkmpadaires). Everything was going perfectly until 2 weeks ago:

It seems that whenever we play on the server, there is a chance that our progress will not be saved ( I haven't found a recurring pattern when it happens). The first time it happened, was after we were 4 players playing on the map for about 3-4 hours on an afternoon. When we came back to play the next day, everything we did was reverted back to an older version of the map, meaning we lost a huge amount of progress, without any explanation or whatever.

I know for a fact it is not "corrupted chunks" as each of us were playing in different areas of the world.

Since this incident, it seems like it will save most of the time, but randomly not save our progress, like yesterday when me (SSBM_Erayz) and pkmpadaires decided to build the walls around our city. We played for quite a few hours until we finished the wall, just to see, oin the next day that all of this progress wasn't saved (the walls we built were in the state they were when we started playing the day before).

Now this is very frustrating, since there is no way to know if our progress will be saved or not.

Is there any reason why a Realm might not save occasionally?