I have to admit that this is a mystery to me. I could not replicate. I can see the issue in the save file, but I can not find the root cause from it. So I'm afraid I won't be able to fix it. If it were to happen again though , let us know

Revelation artefact is deprecated. It reveal the whole map and have an impact on performance. So it's intended. However it not working at all was not, so I fixed at least this part. So old map with revelation artefact will at least work

I'm afraid not. Maybe it has been fix in our internal version.
So I'd suggest waiting for the new patch and see if it is still there : ) (If not bump this post after the patch if you want, or recreate another one ^_)