Impossible to review merge request for files with moderately large changes

Hello,

I am using Gitlab.com and facing the issue in which files with large changes (around 500 changes) cannot be reviewed and there is “Download” button instead of diffs between files. Please take a look at the screenshot below:

I have tried my best to find a settings to disable this button have not been successful. As far as I can remember we haven’t faced this issue before, maybe there is a change recently that I am not aware.

Thanks for reading.