Issue with block content editor resolved by updating Sanity Studio

import {defineType} from 'sanity'

export default defineType({
  title: 'Content',
  name: 'richText',
  type: 'array',
  // All possible "Blocks" that a content editor can use
  options: {
    sortable: true,
  },
  of: [
    {
      type: 'block',
      styles: [
        {title: 'Normal', value: 'normal'},
        {title: 'Heading 2', value: 'h2'},
        {title: 'Heading 3', value: 'h3'},
        {title: 'Heading 4', value: 'h4'},
        {title: 'Heading 5', value: 'h5'},
      ],
    },
    {
      type: 'image',
      icon: () => '🖼️',
      options: {hotspot: true},
      fields: [
        {
          name: 'alt',
          type: 'string',
          title: 'Alternative text',
          description: 'Describe the image. Important for SEO and accessiblity.',
        },
        {
          name: 'wide',
          type: 'boolean',
          title: 'Wide Image?',
          description: 'Makes images wider than the text column.',
          initialValue: false,
        },
        {
          name: 'background',
          type: 'boolean',
          title: 'Add grey background?',
          description: 'Adds a grey background/border to the image.',
          initialValue: false,
        },
      ],
    },
    // Rest of my blocks
  ],
  validation: (Rule) => Rule.required(),
  group: 'content',
})

Could not validate the resulting portable text to insert. Editor value must be an array of Portable Text blocks, or undefined. Try to insert as plain text (shift-paste) instead.