#Solution Found!
Dear Ehamloptiran,
your use of the function GetMaxRHIFeatureLevel( ) is what saved the day for me!
This crashed for me
FileBrowserCanvas = new FCanvas((FTextureRenderTarget2DResource*) FileBrowserRenderTex->Resource,NULL, GetWorld(), ERHIFeatureLevel::SM4 );
this does not
FileBrowserCanvas = new FCanvas((FTextureRenderTarget2DResource*) FileBrowserRenderTex->Resource,NULL, GetWorld(), GetMaxRHIFeatureLevel( ) );
For some reason when I was arbitrarily choosing a feature level this confused UE4, but when I use GetMaxRHIFeatureLevel it works fine!
#Thanks Again Ehamloptiran!