Realms - The server rolls back

I play on a Java realm. It's quite old, created in 2018. We recently ported a survival world over from minehut, where the world kept rolling back and lagging. We expected the world to do a lot better in the realm.
We played on the world in the realm for a full day, wihout much issue. However, yesterday, the realm crashed, and today we find that the server has rollbacked at least 1h-1h30. The realm owner has not loaded a previous save, this is the realm doing it on its own. Is this an issue with the save or the realm?
I know this issue exists on bedrock realms, but i've never heard of it happening on Java. Is there a fix? If this keeps happening, the realm will be quite unplayable, which is a shame.