Long story short: I wrote some code for the workbenches that ended up preventing the server from saving the game if it initated a save while someone was in the process of experimenting.
We tried long and hard all night to come up with a solution, including writing injector programs to modify the memory of the server to bring its save functionality back to life, but to no avail.
Any server that did not have an unlucky timing should be fine, but servers that saved during that 5 second window are screwed.
When stuff like this happens, it makes me second guess our 'weekly patch' approach. While we have a pretty good track record, moving forward and out of early access this kind of thing isn't really acceptable. Even when we don't have a major wipe-requiring issue, sometimes we have to cram stuff into the patch that probably isn't ready for primetime so you guys are getting sub-standard content. I think we really need to re-evaluate our decisions here and consider putting a feature-locked patch on a separate branch that can be tested for a solid week before being pushed out.
We're so sorry.