UATHelper: Cooking (Windows): LogInit: Display: LogObj: Error: LoadConfig (/Script/Engine.Default__RendererSettings): import failed for bEnableAlphaChannelInPostProcessing in: False
bump! same! updated to 4.20 and got this, project wont build
Me too!!!
Change r.PostProcessing.PropagateAlpha=False to r.PostProcessing.PropagateAlpha=0 in defaultengine.ini.
Worked. Thank you!
I figured it out for my project.
Open your project settings in the search at the top put in the word alpha this should filter the options so you can see the top choice:
post processing
The first choice should be Enable alpha channel support in post processing (experimental)
When you see this drop down box it was disabled, for me I choose the first choice not knowing what it did, (LINEAR COLOR SPACE ONLY) and my project built. This is all I changed to fix it.
It requires a restart of the editor and will recompile all of your shaders.
Please note the 3rd choice is (ALLOW THROUGH TONEMAPPER) I haven’t tried this choice it might also work.
Added note: What this does is change the word FALSE to the number 1 in the defaultengine.ini under the setting r.PostProcessing.PropagateAlpha= Was the word (FALSE) requires the numbers 0,1,2 for the different settings mentioned above in the drop down menu. I am 95% sure this changed because they finished this feature, and now had the new options that were not required in previous versions of the engine.
r.PostProcessing.PropagateAlpha=0 in defaultengine.ini is the right answer!
the engine is now stuck on 45% loading… after restart.
the engine is now stuck on 45% loading… after restart.
Hi, the engine is not stuck, when you restart editor, it recompile all the shaders and it take time. about 20/30 min if you have a lot of shaders ! open your taskbar and check if the engin is loading 
This worked for me in 4.20 binary! Thanks for posting.
Give it some time. It gets stuck there the first time when it has to do the shaders all over again I think, but after an hour mine finished loading.
In another thread somebody pointed out that temporary disabling windows defender real time protection greately improves the compiling speed, I did a few tests and I can confirm it works.
“35% bug” is a classic. It’s the shaders recompiling, so it takes forever.
Windows defender realtime protection is what has been costing me hours and days of development time? I think i will turn it off permanently if I can safely do so.
and a good tip is open your task monitor(ctrl+alt+del) and you will see ue4 used all cpu cores, normally means it’s running hard instead of stucking~
thank you so much for your port, it worked.