Warning: Undefined array key "provider" in block_theme_suggestions_block() when flippy block is placed

@Anybody: long holding issue here :) Maybe it isn't reproducable for you no more now. But I would like to inform that this happens without Flippy being installed here so I assume that we are close to inverstigate another issue, which can randimly affect many projects, maybe caused on other places or caused by methods used in contrib whicih need to be changed. Any news on yours?

Possibly related:
✨ Custom blocks cannot be properly exported and imported Active
Possible interesting contribs:
https://www.drupal.org/project/recreate_block_content →
https://www.drupal.org/project/fixed_block_content →

I had the same problem. The warnings came after every time I flushed all caches.

I think the problem is the same in this module. More precisely:

• in file: flippy\src\Plugin\Block\FlippyBlock.php
• in function: public function build() {
• in the building of the variable $build

The $build variable currently doesn't have this: '#configuration' => ['label' => $block->label(), 'provider' => $provider, ...

.. And a lot of Drupal core modules have code that want this $provider value (like core/modules/block/block.module):

/**
 * Implements hook_theme_suggestions_HOOK().
 */
function block_theme_suggestions_block(array $variables) {
  $suggestions = [];

  $suggestions[] = 'block__' . $variables['elements']['#configuration']['provider'];

Thanks @hanneshh but looking at the code I don't think flippy is doing anything wrong there?
Back to postponed until we have clear steps for reproduction and can say what's causing this... I'm also unsure if flippy is causing this or not.

I have this problem on 2 projects now... Must be related to core somehow...

@DudeWeb: Do you have flippy installed on both?

@DudeWeb @Anybody, i think the issue is with twig tweak when calling blocks.
Instead of calling your blocks as drupal_block('block_name'), you should be using drupal_entity('block', 'block_name')