[2019] 342.5MB update just now?

Update: April 23, 2019
We are really sorry, but we had to temporarily revert back to Unity 2018.1 (Alpha 9.6 - Build 2307) since UNET causes some problems that we need to address first. Your save games should be fully compatible with Alpha 9.6.

Alpha 9.7 (Build 2316) will stay on the EXPERIMENTAL branch.

https://steamcommunity.com/games/383120/announcements/detail/1633027651915312436

Originally posted by VulcanTourist: Doesn't Eleon have closed testers who get first crack at everything?

Yes but this kind of issue unfortunately doesn't appear until a server becomes highly populated.