Also, after updating my servers (multiple independent servers), they started crashing the KF2 games of players upon joining the lobby. The servers themselves run fine. So far I've narrowed it down to something in either *engine.ini and *kfgame.ini files on the KF2 servers, which I haven't changed for a while. If I delete these to allow the game to recreate them from the default ones, it works just fine.
I bet this happens to more than one server owner, as I haven't really done anything fancy with the config files, outside of regular motd, serverbanner, server name and mapcycles modifications.
It's something in the *kfgame.ini file. *kfengine.ini is fine.
The clients crash with this bugsplat:
Assertion failed: i>=0 && i<this->ArrayNum [File:d:\kf2\depot_kf2\kf2_staging\development\src\core\inc\Array.h] [Line: 2076]
Stack: Address = 0xeae4be09 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xebb53780 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xebb7d6d8 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xeb312868 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xeb85f0e1 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xebabe00c (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xebab8660 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xebab86aa (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xebac01b0 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xec1210bf (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xd4517614 (filename not found) [in C:\Windows\System32\KERNEL32.DLL]
Address = 0xd5e826a1 (filename not found) [in C:\Windows\SYSTEM32\ntdll.dll]
Address = 0xd5e826a1 (filename not found) [in C:\Windows\SYSTEM32\ntdll.dll]
Address = 0xd360cd29 (filename not found) [in C:\Windows\System32\KERNELBASE.dll]
Address = 0xeae88dc5 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xeae3d805 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xeae4be7c (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xebb53780 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xebb7d6d8 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xeb312868 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xeb85f0e1 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xebabe00c (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xebab8660 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xebab86aa (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xebac01b0 (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xec1210bf (filename not found) [in C:\Program Files (x86)\Steam\steamapps\common\killingfloor2\Binaries\Win64\KFGame.exe]
Address = 0xd4517614 (filename not found) [in C:\Windows\System32\KERNEL32.DLL]
Address = 0xd5e826a1 (filename not found) [in C:\Windows\SYSTEM32\ntdll.dll]
Address = 0xd5e826a1 (filename not found) [in C:\Windows\SYSTEM32\ntdll.dll]
PS Okay, I've narrowed it down to the BannerLink parameter in the kfgame.ini KF2 server file. BannerLink points to a web server that hosts a MOTD picture. This picture gets downloaded by the KFHTTPImageDownloader class, which uses the native DownloadImageFromURL the code of which isn't shared with the SDK.
My guess is you changed something so it now crashes KF2 clients when they join a server which hosts a banner image that doesn't fit for whatever reason. I suspect it's the case, because there were issues recently with console players crashing with other players avatar pics. This function is also used to download them. Molly and Yoshiro, did you touch this function?
Can you develop a graceful handling of it instead so the clients don't crash if they can't download it?
Can you be more transparent about the new requirements for MOTD banners so we don't have to guess which work?