Cannot override template provided by contrib module in theme I'm leveraging the Superfish module for our menus but need to tweak the output a bit.
Normally I'd just copy the relevant template file (in this case superfish-menu-items.html.twig) into my theme and call it a day.
This isn't working in this case. Any ideas why that might be and how to get around it? 

Before voting to close this issue, I'd ask that you request information you think would be valuable to providing additional specificity.
I can only assume that this issue is due to some issues with the construction of the Superfish module itself and its theming implementation, so I'm trying to figure out how to work around this.
Any solution would likely be applicable in similar contexts as well.

I've tried modifying the element in hook_theme() and hook_theme_registry_alter() to point to my theme's implementation of the template, but in both cases I end up hitting


  Twig_Error_Loader: Template is not defined errors.


EDIT: I'd already enabled debugging prior to posting. Please stop suggesting that I enable debugging. This is what is shown before and after copying the template into my theme. I've cleared caches and verified the template name in my theme.
For drupal8 you need to enable twig debug in the service.yml file. Then clear cache. After that, you will see in the browser inspector all templates name suggestion to override a part of the page.