Preview Fails to render zoom properly for large png
I would try to open the image in a brand new user account, you can set that up in System Preferences > Users &amp; Groups or just use the Guest account. If you see different results here it must be something in your profile interfering with Preview.

But I'm betting the preview developers didn't account much for people opening 49MB, 32kx32k images. In the likely chance that this is a genuine glitch you could quickly report it at https://www.apple.com/feedback/ or sign up for a developer account &amp; do a full bug report over at https://developer.apple.com/bug-reporting/. 

In the short term I would recommend trying to use a different application to view this. A browser or photo editing application might be a good fit. For an image like this there is also a good chance that JPEG would more efficiently compress it &amp; cause less issues, maybe look into converting it with Photoshop or similar.