Image Blocks in posts returning "invalid_blocks" error.

Trying to add some images to chat post message and anytime I place the image blocks into the JSON object sent, I get an error of "invalid_blocks".

If I remove the 3 nodes with "type":"image" from the following JSON object, the post works just fine. I'm using $slackClient->chatPostMessage([...]); to send the message.

Using version 4.5.

Following is the JSON... I have obscured the image urls below.

[
  {
    "type": "header",
    "text": {
      "type": "plain_text",
      "text": ":birthday: Today's Birthdays:"
    }
  },
  {
    "type": "section",
    "text": {
      "type": "mrkdwn",
      "text": " - Employee 1 - 08/07\n"
    }
  },
  {
    "type": "divider"
  },
  {
    "type": "header",
    "text": {
      "type": "plain_text",
      "text": ":star: Today's Work Anniversaries:"
    }
  },
  {
    "type": "section",
    "text": {
      "type": "mrkdwn",
      "text": "- Employee 2 - 17 Years\n"
    }
  },
  {
    "type": "divider"
  },
  {
    "type": "header",
    "text": {
      "type": "plain_text",
      "text": ":no_entry_sign: On PTO Today:"
    }
  },
  {
    "type": "section",
    "text": {
      "type": "mrkdwn",
      "text": "- Employee 1 from 1:00 pm to 3:00 pm CST\n- Employee 3 - all day\n"
    }
  },
  {
    "type": "divider"
  },
  {
    "type": "header",
    "text": {
      "type": "plain_text",
      "text": ":newspaper: Today's Posts:"
    }
  },
  {
    "type": "section",
    "text": {
      "type": "mrkdwn",
      "text": "*Test Post #1* / _Employee 1_\n_This is just a test. It is only a test. _\r\nhttps://youtube.com\n\n"
    }
  },
  {
    "type": "image",
    "image_url": "https://s3.XXXXXX.com/uploads/64d146c7da835111239138.png",
    "alt_text": "Test Post #1"
  },
  {
    "type": "section",
    "text": {
      "type": "mrkdwn",
      "text": "*Test Post #1* / _Employee 1_\n_This is just a test. It is only a test. _\r\nhttps://youtube.com\n\n*Morning Post Test #2* / _Employee 1_\nThis is just a test. Trying out an image.\n\n"
    }
  },
  {
    "type": "image",
    "image_url": "https://s3.XXXXXX.com/uploads/64d1436751356448563628.jpg",
    "alt_text": "Morning Post Test #2"
  },
  {
    "type": "image",
    "image_url": "https://s3.XXXXXX.com/uploads/64d144e78c178766939002.jpeg",
    "alt_text": "Morning Post Test #2"
  },
  {
    "type": "divider"
  }
]

Stack Trace:

An error occurred when trying to run the Good Morning Slack Post: JoliCode\Slack\Exception\SlackErrorResponse: Slack returned error code "invalid_blocks" in /Users/grayloon/Sites/loons/grayloon/vendor/jolicode/slack-php-api/src/HttpPlugin/SlackErrorPlugin.php:41
Stack trace:
#0 /Users/grayloon/Sites/loons/grayloon/vendor/php-http/httplug/src/Promise/HttpFulfilledPromise.php(31): JoliCode\Slack\HttpPlugin\SlackErrorPlugin->JoliCode\Slack\HttpPlugin\{closure}(Object(Nyholm\Psr7\Response))
#1 /Users/grayloon/Sites/loons/grayloon/vendor/jolicode/slack-php-api/src/HttpPlugin/SlackErrorPlugin.php(42): Http\Client\Promise\HttpFulfilledPromise->then(Object(Closure))
#2 /Users/grayloon/Sites/loons/grayloon/vendor/php-http/client-common/src/PluginChain.php(44): JoliCode\Slack\HttpPlugin\SlackErrorPlugin->handleRequest(Object(Nyholm\Psr7\Request), Object(Closure), Object(Http\Client\Common\PluginChain))
#3 /Users/grayloon/Sites/loons/grayloon/vendor/php-http/client-common/src/Plugin/ErrorPlugin.php(62): Http\Client\Common\PluginChain->Http\Client\Common\{closure}(Object(Nyholm\Psr7\Request))
#4 /Users/grayloon/Sites/loons/grayloon/vendor/php-http/client-common/src/PluginChain.php(44): Http\Client\Common\Plugin\ErrorPlugin->handleRequest(Object(Nyholm\Psr7\Request), Object(Closure), Object(Http\Client\Common\PluginChain))
#5 /Users/grayloon/Sites/loons/grayloon/vendor/php-http/client-common/src/PluginChain.php(59): Http\Client\Common\PluginChain->Http\Client\Common\{closure}(Object(Nyholm\Psr7\Request))
#6 /Users/grayloon/Sites/loons/grayloon/vendor/php-http/client-common/src/PluginClient.php(87): Http\Client\Common\PluginChain->__invoke(Object(Nyholm\Psr7\Request))
#7 /Users/grayloon/Sites/loons/grayloon/vendor/jolicode/slack-php-api/generated/Runtime/Client/Client.php(82): Http\Client\Common\PluginClient->sendRequest(Object(Nyholm\Psr7\Request))
#8 /Users/grayloon/Sites/loons/grayloon/vendor/jolicode/slack-php-api/generated/Client.php(1806): JoliCode\Slack\Api\Runtime\Client\Client->executeEndpoint(Object(JoliCode\Slack\Api\Endpoint\ChatPostMessage), 'object')
#9 /Users/grayloon/Sites/loons/grayloon/src/Controller/MorningPostController.php(417): JoliCode\Slack\Api\Client->chatPostMessage(Array)
#10 /Users/grayloon/Sites/loons/grayloon/src/Controller/MorningPostController.php(390): App\Controller\MorningPostController->postToSlack('@rwade', Array)
#11 /Users/grayloon/Sites/loons/grayloon/vendor/symfony/http-kernel/HttpKernel.php(163): App\Controller\MorningPostController->goodMorningAction(Object(Symfony\Component\HttpFoundation\Session\Session))
#12 /Users/grayloon/Sites/loons/grayloon/vendor/symfony/http-kernel/HttpKernel.php(74): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1)
#13 /Users/grayloon/Sites/loons/grayloon/vendor/symfony/http-kernel/Kernel.php(184): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#14 /Users/grayloon/Sites/loons/grayloon/public/index.php(25): Symfony\Component\HttpKernel\Kernel->handle(Object(Symfony\Component\HttpFoundation\Request))
#15 /Users/grayloon/.composer/vendor/laravel/valet/server.php(234): require('/Users/grayloon...')
#16 {main}

jolicode / slack-php-api

Image Blocks in posts returning "invalid_blocks" error. #160