Gmod sandbox server borked by yet another steam update

Both Gmod and Steam have been updated and yet again it has borked both clients and the server. Noticeable breakages are ULX, Simple Prop Protection and Aprilonscript's custom scoreboard. Clients are also getting a lot of "Server uses different class tables" disconnects.

Here's my console log from my latest session.

Commencing connection retry to 195.90.98.23:27015
Connecting to 195.90.98.23:27015...
Connected to 195.90.98.23:27015

Sandbox
Map: gm_flatgrass
Players: 11 / 14
Build: 3943
Server Number: 1

ConVarRef wr_ignoregroups doesn't point to an existing ConVar
SetConVar: No such cvar ( wr_ignoregroups set to superadmin;admin;operator), skipping
ConVarRef wr_sandboxonly doesn't point to an existing ConVar
SetConVar: No such cvar ( wr_sandboxonly set to 1), skipping
No pure server whitelist. sv_pure = 0
Decompressing data pack into virtual file system..
Unable to read pack file: cache/a462e1ecadb1ccbdb8d8cad26de2d7e4.dua
Unable to load virtual file system!

Lua initialized (Lua 5.1)
======== Installing Table (De)Serialiser Module | ver: 1.4 ========
RunConsoleCommand blocked - sent before player spawned (sv_tags)
======== Beam NetVars Lib v0.71 Installed ========
--- Missing Vgui material ignore_this_error
loading materials
loading material: cable/rope_icon
loading material: cable/cable2
loading material: cable/xbeam
loading material: cable/redlaser
loading material: cable/blue_elec
loading material: cable/physbeam
loading material: cable/hydra
loading material: arrowire/arrowire
loading material: arrowire/arrowire2
=== Loading Wire Model Packs ===
	Loaded: PHXWireModels.txt
	Loaded: default.txt
	Loaded: expression2.txt
	Loaded: bull_buttons.txt
	Loaded: cheeze_buttons2.txt
	Loaded: wire_model_pack_1.txt
	Loaded: wire_model_pack_1plus.txt
	Adding Cheeze's Buttons Pack
	Adding various Buttons from HL2 and Portal
	Jaanus' Thruster Pack
	Beer's Model pack
ERROR! Module 'zlib_b64' not found!
==== Advanced Duplicator v.1.72 shared module installed! ====
==== Advanced Duplicator v.1.741 client module installed! ====
OPENING FALCO'S SCRIPTS!
Registering gamemode 'sandbox' derived from 'base'
Loading Wire Tools
--- Missing Vgui material texturemissing
Sending 1057 'User Info' ConVars to server (cl_spewuserinfoconvars to see)
Player ***Nazi #3*** has joined the game
[UCL] Access set.
:1: attempt to index global 'Stream' (a nil value)
:1: attempt to index global 'Stream' (a nil value)
[UCL] Access set.
AdvDupeShared: Server Compression: false
RunConsoleCommand blocked - sent before player spawned (ZLib_Installed)
Redownloading all lightmaps
Profile is loading...
Unknown command: spp_pgr
Unknown command: spp_dpd
Unknown command: spp_edmg
Unknown command: spp_admin
Unknown command: spp_awp
Unknown command: spp_check
Unknown command: spp_dae
Unknown command: spp_delay
Unknown command: spp_use
Profile has been loaded!
:1: attempt to index global 'APN' (a nil value)
๖ۣۜBogi ๖ۣۜTechno: HI
Warning: Unhandled usermessage 'ULibUserUCL'
Unknown command: spp_pgr
Unknown command: spp_dpd
Unknown command: spp_edmg
Unknown command: spp_admin
Unknown command: spp_awp
Unknown command: spp_check
Unknown command: spp_dae
Unknown command: spp_delay
Unknown command: spp_use
:1: attempt to index global 'APN' (a nil value)