Drupal 8.x

I have wasted about a month trying to fix this error on a site. I Googled everything, to no avail. Uninstalling and reinstalling the media module did NOT fix this error. Nor did reenabling the media view because it did not exist on my Drupal 8.8.2 site. I had previously switched from media to media_embed, which probably caused this, but fixing it was really obscure.

This might not be fully related to Drupal... but... I'm using the Drupal VM vagrant environment to develop with Drupal. I use xdebug a lot and sometimes (very rarely) xdebug refuses to trigger when I add a breakpoint in code. So I'll keep refreshing the site page in the browser to trigger xdebug but nothing happens, however, if I then clear the Drupal site cache (using drush cr on the command line) then xdebug immediatly works as expected on the next page refresh.

I have in Drupal 8.7.11 two Content type:
1.Hotel (machine name: hotel) and 2.Room (machine name: room)
and two Vocabulary: 
1.Payment method, (with Terms: Cards and Cash) and 2.Number beds, (with terms: 1, 2, 3 and 4)

Hotel fields are: 
1. field_payment_method Entity reference to Vocabulary: Payment method, Type of item to reference: Taxonomy term, Allowed number of values: Unlimited
2. field_connected_room Entity reference to Content type: Room, Type of item to reference: Content, Allowed number of values: Unlimited

Hi, I've created a new field "nickname" in user account settings. I want to use custom validation constraint (https://www.drupal.org/docs/8/api/entity-api/entity-validation-api/providing-a-custom-validation-constraint) to make this field unique but I don't know what hook to use to add the constraint. Do you have any idea or alternative? Thanks!

I am working on a site to track my daily carbohydrate intake. I can represent a Food item that I might eat, say a taco as a Content Type. I would call it 'Food' and it would have fields for name, description, and # of carbs.  The problem comes with representing a meal. For a given meal, say Monday Lunch, I could eat several tacos and a burrito. I can't quite see what Content Type could hold entity references to multiple different Food nodes as well as an amount eaten of each Food node.