I get this issue using Views module:
Symfony\Component\Routing\Exception\InvalidParameterException: Parameter "arg_0" for route "view.test.feed_1" must match "[^/]++" ("" given) to generate a corresponding URL. in Drupal\Core\Routing\UrlGenerator->doGenerate() (line 205 of /code/web/core/lib/Drupal/Core/Routing/UrlGenerator.php).
How to recreate it:
1. Create view with a block display.
2. Add filters to the block, expose them to visitors and enable AJAX.
3. Add page display with contextual filters and the path should have a dynamic argument such as /path/%.
4. Place the block to any page then you will get the issue.
The reason of that is views module wants to replace form action with page url and the url is broken because it doesn't have any argument.
I used Better Exposed Filter and didn't check the issue without it though.