Well there is always some shit of this kind when development goes by 1 man so thats ok, in addiction he had some problems so it's just better to be tolerant.
Here's the thing you have to understand,
The bigger the game is, there's more bugs to consider about.
More features = More time needed to implement it + Figuring out and fixing the bugs
Therefore deadlines are just an unrealiable way to measure time in game development, or more accurately, in any kind of programming projects.