ember-cli-fastboot beta versions work, but rc causes 500

[Redsandro]

I was running ember-cli-fastboot v1.0.0-beta.13 for a little over a year. And now when I try to update, I'm getting an internal server error from the server.

So I tried to upgrade one version at a time and do a deploy. I noticed I can update all the way to v1.0.0-beta.19 without a problem, but the next release (v1.0.0-rc.1) causes a request to the website to return an internal server error.

Is there a known breaking change between the latest beta and the first rc that can help me figure out what causes this?

I'm still at Ember-cli 2.0.7 because of dependencies on certain plugins that aren't frequently updated, but haven't had any trouble before.

Using nginx to proxy_pass fastboot-app-server. The fastboot-app-server version seems irrelevant.

[Redsandro]

I learned through #387 that it's because of gmurphey/ember-masonry-grid#58.