Issues with 3D printing bend corners

[Bir3D]

Hello,

I’ve modelled a phone case, but when I print it, I run into some strange issues, namely that 2 of the bend corners are not getting printed.

I’m not sure in what part of the chain the issue occours. In the attached picture I’ve highlighed the sides not gettting printed. Every face is the correct way, and the edges are connected. It’s also very odd that the print is stright, whereas in the google skecthup model, the connected is skewed, possibly the 3D printer itself is the isse?

Anyone got any suggestions for what the issue could be?

Cheers.