If It Ain't Broke Don't Fix it!

Why is it practically every new build Epic has to make changes to materials and meshes that mess up all maps using them?

Here's a recent example where for some reason they just had to screw with M_Chill_StoneWall_05 in the May 24 build.

In Editor...

Though the reddish wood looks different (brighter, more saturated color) than before, the wall material looks pretty much the same as it always has. It looks good.

But load the map in game and it's a different story altogether...

It looks like complete crap... A material I've been using for months, that's looked fine, and still looks fine in the editor, looks terrible in game. Making matters worse, I tried fixing this by using another material, but it has the same problem!

Of course it's possible it's an obscure new bug rather than an actual change to the materials but still, why do they constantly keep changing and breaking things like this?

If it ain't broke, don't fix it!

Update:

I found several materials (mostly variations on 3 wall materials in the Chill assets) doing this. Affected maps include Codex, Malevolence and Gothic.

I might start using more custom (non-stock that is) materials and meshes like the ones from various UT4 tech demos simply because there aren't any problems with them changing and breaking maps every 2nd build! Yes, the pak files will be larger but at least they won't break every time someone at Epic arbitrarily decides to change things that weren't broken.