If it happens on fresh start with Doom on loading screen, and does not happen until restart after Living Quartz shows there, then it is likely this one: [Investigating] Game Freeze in Training
If you are on Windows, check if Player.log
in %userprofile%\AppData\LocalLow\Pipeworks\GemsofWar
contains something like
NullReferenceException: Object reference not set to an instance of an object. at GemColorFunctions.StringContainsColor (System.String value) [0x00000] in <00000000000000000000000000000000>:0 at PuzzleTrait.DoTrait (System.Object pTarget, TraitParams value) [0x00000] in <00000000000000000000000000000000>:0 at PuzzleTrait.ActivateTrait (System.Object pTarget, TraitParams value) [0x00000] in <00000000000000000000000000000000>:0
near end