https://pastebin.com/YiuAgb2J *** Error: Skybox vtf files for skybox/sky_dustbowl_01 weren't compiled with the same size texture and/or same flags! Can't load skybox file skybox/sky_dustbowl_01 to build the default cubemap! Hammer keeps giving me that error, whether I use a HDR skybox or not, which was suggested by Interlopers when I pasted the log in. I verified the TF2 files through steam, same problem. Any ideas? I'm also certain that the map is sealed.
The error is that vbsp is dumb and doesn't understand cubemaps with different resolutions for the sides. All it does is failing to use the skybox as the default cubemaps, resulting in the classical pink reflections. But you were going to build the cubemaps anyway, so it doesn't matter.