Required Relation Field

Thanks a lot for your detailed explanation. I will check the debugging soon.

For my example code: Yes this is a model with publishing enabled. After your feedback I tried the following code and it seems to work:

async beforeUpdate(params, data) {
      if(data.published_at && !data.title) {

        const article = await strapi.query('article').find({id: params.id});

        if(article[0].article_category === undefined || article[0].article_category === null) {
           throw new Error('Entity is required!');
        }
      }
      else if(!data.published_at && data.title) {
        if(data.article_category === undefined || data.article_category === null) {
          throw new Error('Entity is required!');
        }
      }
    },

Or do you see any mistake in it?

Thanks for your help!