I deleted and reinstalled 5.5.1 from scratch to triple check there’s no issue with the installation integrity (missing files and such).
Opening freshly installed EGS version of 5.5.1 and creating a blank project throws about 10 warnings about missing .png resources:
Having FAB plugin enabled throws another warning on top:
And opening material editor throws another ~30 warnings about missing .png resources:
So if you are a new user, install official version of the engine from EGS launcher, create project from Epic’s own “Blank” template, open it, and just open material editor, this is the amount of log warnings you have to deal with:
On top of that, if you just change the editor layout and save it under any name, you get even more:
It’s like nearly every editor operation, no matter how essential, as simple as opening the material editor or saving editor layout has the output log screaming at you with yellow messages that you are doing something wrong, while there’s nothing you can do to solve it.
This is really, really, I do mean really low quality standard for public product release for the corporation the size of Epic 
And it teaches both new and existing users that log warnings are okay and should be ignored because you can’t do anything about them, which is extremely bad practice.