Here is what they had to say about it to the Kickstarter backers:
As we’re approaching the finish line, we’ve come across some details in the game that we really want to address. Some of the issues are about tuning, while others are straight-up bugs fixes. Since we owe it to every one of you to give you the best possible game we can make, we’ve decided to push back the game’s release date to September 8th.
We’ve enjoyed and appreciated your overwhelming support throughout this whole production, and we want you to be proud of the game that you’ve backed. Mike and I both feel like releasing the game without addressing the last of these issues would be falling short of that.
Thanks everyone — the adventure begins September 8th!
Armikrog will release September 8 for PC, Mac and Linux. The Wii U version will be released at a later date.
Source: Press Release