I work in a Github repo that checks in many non-plain text files and sometimes my PRs will fail to display the rich diff with the cryptic message:

Sorry, something went wrong. Reload?

Not very helpful right? Especially when reloads have a 50/50 chance of fixing the issue. Until Github addresses this issue there are a few ways to work around this.

The first is to download the file and check it manually. Not the best but works.

The second way, which works in my case, would be to allow everything to load(and fail) then switch to display the source diff then back to display the rich diff.

As far as I can tell the problem is Github is failing to load the larger files correctly. Especially when loading multiple of them at the same time. Fingers crossed we get a fix soon.