Hi GlacierFox,
As others have said, this appears to be a case of a Blueprint which somehow became corrupted. We’re sorry it happened, and would like to take a look at the Rangefinder.uasset if you’d be willing to share it with us. This way we could find the failure and try to prevent it from happening again.
In the meantime, you should be able to get back into the project by removing that .uasset from your content folder and/or changing your default map which loads (so the Blueprint doesn’t try to load automatically).
Cheers