At a guess something about your blueprints are corrupted. I’d go through and recompile every blueprint and see if you can kick it into having an error, ESPECIALLY UMG blueprints. Try to compile in order of widgets that are embedded, back to standalone widgets. These are about the only things I’ve had fail like this.
Also, as a second step you should always find the build command in the log and run it in the command line yourself, as you’ll get more verbose output and often a lot more info about the error. You’ll need to navigate to where the UBT is and run it with the arguments from the log.