Hi, you can increase the "timeout" in sourcemod\configs\core.cfg file as a workaround, although it is not recommended.
Code:
/**
* If a plugin takes too long to execute, hanging or freezing the game server in the process,
* SourceMod will attempt to terminate that plugin after the specified timeout length has
* passed. You can disable this feature by setting the value to "0".
*/
"SlowScriptTimeout" "10"
The error may occur depending on how many campaigns you have installed or if the server is being slow to read the files.