Supplement:
Please watch the movie.
https://www.dropbox.com/s/even74fvu8i7xnq/Mecabricks-Bug.mov?dl😮

The video helps identifying the issue. After going fullscreen, your brick is larger than it was before. So, the browser you're using is zooming the screen to fit it instead of realigning everything. To make sure it's this, try moving your mouse until one of the arrows is highlighted, then click & drag.

Using an other browser is the solution for now, possibly it can be resolved if the viewport of Mecabricks is extended. (That last thing can only be done by Scrubs. )

Hello,

I have an iMac 5K too which I use to develop Mecabricks.
I have the same issue with Safari. It looks like that from a certain size of the window it is lost with the ratio, actually before it becomes full screen. Slowly enlarge the window and the problem will be amplified once it reaches a special size. It does also happen with other webapps that use three.js

I stopped using Safari now for Chrome.

I also came to the same realization.
Have a look at brickset.com and watch any LEGO model (for examle set 21306, the "Yellow Submarine", the highlight of 2016) in the "3D View". This service is supported by Mecabricks and you will see the same bug.

I know. The 3D View tab in Brickset is my idea 😛 This is the exact same 3D player on both websites ( which I made). Brickset is displaying the Mecabricks sets that I tagged as Official.

@ Scrubs
Thank you so much for your services. Brickset is my most loved and used LEGO-Site.
Till now i 've been using LDD, but now i've to change and work with Mekabricks. I don't matter about the bug with the Safari-5K, i better use Firefox.

Thanks 😉