Fansub encoders usually use a constant rate factor (constant quality) and not a constant bitrate. This causes file sizes to vary for the reasons explained by Leggy.
Streaming services (CrunchyRoll, Hulu, Daisuki, etc. — files ripped by HorribleSubs) on the other hand use a constant bitrate, leading to very uniform file sizes.
You could always use Hiryuu's version until FFF's is released. I did have some weird subtitle issues in it though (the subs were inconsistent until after the opening).
Sorry again for adding to the list, but you're the only one left with this. Please reupload when you have the time, thanks. みずカノ
Also, could you update this to Ver1.31? It wasn't listed, but it definitely got updated. 隷属と解放のラビリンス