Hi Zakku,
Sanctum 2 is powered by UE3 not UE4 
From what you say, it sounds like the keys are not registering the first time you press them.
- Confirm that you don’t have those keys input nodes anywhere else in the BP, or that they are not set to consume the input exclusively
- Confirm that the window has focus - try clicking your mouse inside it before you test the keys.
If it still doesn’t work, please post you relevant blueprint sections.