I have noticed that QuestManager::spawn_from_spawn2 is checking the database key (GetID) rather than the spawngroup ID.
This might be intended, but I have changed my copy to use the spawngroup id when spawning a mob. A diff against the current GIT for questmgr.cpp:
Code:
299c299
< if(cur->GetID() == spawn2_id)
---
> if(cur->GetSpawnGroupID() == spawn2_id)