Oddly, installing the latest xcode fixed the issue on some of my projects but not my major one, which still crashes in the splash screen. The Console throws a bunch of texture issues before eventually closing the process.
default 20:40:21.747230 -0700 BlankBase [2018.09.23-03.40.21:746][ 0]LogTexture: Error: Texture2D /Game/EternalTemple/Textures/T_Temple_Railing_01_N.T_Temple_Railing_01_N is unknown [raw type 0] which is not supported.
default 20:40:21.747287 -0700 BlankBase [2018.09.23-03.40.21:747][ 0]LogTexture: Error: Texture2D /Game/EternalTemple/Textures/T_Temple_Railing_01_M.T_Temple_Railing_01_M is unknown [raw type 0] which is not supported.
default 20:40:21.747331 -0700 BlankBase [2018.09.23-03.40.21:747][ 0]LogTexture: Error: Texture2D /Game/EternalTemple/Textures/T_Temple_Railing_01_BC.T_Temple_Railing_01_BC is unknown [raw type 0] which is not supported.
default 20:40:21.750029 -0700 BlankBase [2018.09.23-03.40.21:749][ 0]LogTexture: Error: Texture2D /Game/EternalTemple/Textures/T_Grass_01_N.T_Grass_01_N is unknown [raw type 0] which is not supported.
default 20:40:21.750118 -0700 BlankBase [2018.09.23-03.40.21:749][ 0]LogTexture: Error: Texture2D /Game/EternalTemple/Textures/T_Grass_01_BC.T_Grass_01_BC is unknown [raw type 0] which is not supported.