Laravel 5: Internal error - output before headers, when using a blade view

I'm stuck on an insane error with a Laravel 5.4 view.

I use $contents = View::make("example"); to get the contents of a blade file.

I found out that when there are more than around 6700 characters in the blade file, I get an internal error 500.

When I delete some lines in the blade, even in a comment section, it starts working again.

In the apache logs I found something like "Output before headers : index.php"

What could possibly cause this?!

via Chebli Mohamed