There was a few month fgfs.pid file in my home directory. FG goes into read only mode, he does not build the cache, and probably crash trying to read it.
You should probably wait a few days. I'm optimistically hoping most of this will get cleaned up by the end of the weekend. Lots of discussion and work going on behind the scenes
Remember that the nightly builds are for the cutting edge development repositories. These are unstable, experience incompatible changes, will sometimes just not work (by design), and are in a constant state of flux. But so is life on the cutting edge