I solved the issue.
It was a problem with rack
.
I replaced
use Rack::TryStatic,
:root => File.join(App::SETTINGS.source, App::SETTINGS.site.config['destination']),
:urls => %w[/]
with:
use Rack::Static,
:urls => ["/#{App::SETTINGS.site.config['destination']}"],
:root => File.join(App::SETTINGS.source, App::SETTINGS.site.config['destination'])