Rust Dedicated server - Server crashes after startup

So I've been running a dedicated Rust server for some time, with no issue. I had created a couple different worlds (different seeds with different server identities) and switching between them with no problem. There was a Rust client update today, so I used the steamcmd.exe and app_update as usual, and it said it was successful. However now when I try to load any world (even a brand new one) I get this:

Navmesh Build took 50.18 seconds
Map Spawned 309 entities
Couldn't load server/MyServer/proceduralmap.4000.123456.147.sav - file doesn't exist
Missing EnvSync - creating
Missing CommunityEntity - creating
Missing ResourceDepositManager - creating
Initializing 27541 entity links
Initializing 234 stability supports
Facepunch.Steamworks Unity: WindowsPlayer
Facepunch.Steamworks Os: Windows
Facepunch.Steamworks Arch: x64
Couldn't initialize Steam Server (0)
eac_server.dll [x64] :: hModule: 00007FFF98750000 dwReason: 1 lpvReserved: 0
Server startup complete

E:\SteamGames\rust_server>

I know the sav file not existing is just an artifact of this being a new server, so I'm not worried about that. I've seen from other posts that apparently the eac_server.dll line is okay, people get spammed with that on the console and the server still works, but I never used to get that message before when it worked. Steam just shuts the server down immediately after the Server startup complete message.

If it matters, here is my started line:

RustDedicated.exe -batchmode +server.port 28015 +server.level "Procedural 
Map" +server.seed 123456 +server.worldsize 4000 +server.maxplayers 10  
+server.hostname "My Rust Server" +server.description "My Rust server" 
+server.identity "MyServer"

(broken into multiple lines here just for visibility, single line in the startup file)

Any suggestions would be appreciated.