You should still use Hammer's compiler when you cordon to test something quickly, though. VBCT is something I (and I think most people) use for compiling a release.
Yeah, a lot of that stuff is flaky, especially when Steam is updating itself or games. A lot of "bugs" filed for PackBSP boil down to: "Your SDK is broken. Restart and blame Valve instead."
If this is your first time logging in after the migration (Feb 8, 2022), you must reset your password to log in. Follow this guide if you're having trouble