We've heard your concerns about optimisation and worked on identifying sources of frame drops. Good news! We found that a lot of frame drops were caused by loading sound effects during runtime, so we managed to significantly reduce frequent frame drops due to those.
We'll be monitoring your feedback on the effect those changes had - if you were experiencing frame drops and stutters please let us know if this fixes it. We'll continue to monitor and patch ASAP.
Optimization :
Fixed frequent sources of frame drops due to sound effects being loaded into memory during runtime.
Bug fixes :
Fixed level 3 towers & barricades not being upgradeable to level 4 both in Campaign and Horde Mode. (Shoutout to Cogzworth in the Steam forums for flagging this one to us!)
UPDATE: When we initially released this patch, it caused an issue with black screens on scene loads. We rolled it back and fixed this black screen bug.