Self-made fatty dough separates in refrigerator, how to prevent I'm not sure if this dough has a specific name in English, it consists of 3 parts (by weight) flour, 1 part fat (mix until it consists of small crumbs) and 1 part water (+salt, mix until it's smooth). Used either to wrap around some filling, or as the bottom below the filling. I'm using liquid plant fat (sunflower) for the fat. Recently I tried making a double portion and keeping half in the refrigerator to use later.

But the dough partly separated, i.e. some of the fat ran out.

Where I live this type of dough is readily available in stores and I've never had the separating problem with store bought one.

But the store bought ones usually use butter or hardened plant fats. Apart from using such less healthy and/or non-vegan fats, is there something else I can do to prevent separation?

I would like to emphasize that I'm after some small change or trick to solve my problem, not another kind of dough. No, I'm not preparing it wrong. When used fresh, it's just fine, i.e. the way I want it to be.
I have had this problem before too, and the only solution I have encountered is to freeze the dough you want to store, this requires a bit more planning as you will want the dough to thaw completely before you use it. The best way I have found to thaw the dough is covered on the counter or placed somewhere it can rest without being touched or moved much. I hope this helps and you solve your problem:-)