@gee4: I can only suggest to use PC version when possible. Switch swizzling doesn't work properly for non-square textures in umodel. There are some partial solutions for other games, but only default implementation (which works for square textures) doesn't crash in all possible cases.
Thanks for the reply, I ended up just editing it myself and filling the missing pixels with the PC version.
By the way, I'm trying to edit some text strings as well. I was able to preview some of them with UAssetGUI, but I couldn't find the specific ones I'm looking for. Do you happen to know how to find them? If there's some way to make a search for a string and somehow it points you to the .uasset files that contains it?