When turning cache off, an error page is shown

When disabling cache following the instructions presented on https://www.drupal.org/node/2598914 , when loading a page the site throws the following error:

The website encountered an unexpected error. Please try again later.

AssertionError: Cache Tags must be strings. in Drupal\Component\Assertion\Handle::Drupal\Component\Assertion\{closure}() (line 197 of core/lib/Drupal/Core/Cache/DatabaseBackend.php).
assert('\Drupal\Component\Assertion\Inspector::assertAllStrings($item['tags'])', 'Cache Tags must be strings.') (Line: 197)
Drupal\Core\Cache\DatabaseBackend->doSetMultiple(Array) (Line: 164)
Drupal\Core\Cache\DatabaseBackend->setMultiple(Array) (Line: 154)
Drupal\Core\Cache\DatabaseBackend->set('beautytips:beautytips-ui-custom-tips', Array, -1, Array) (Line: 152)
beautytips_manager_get_custom_tips() (Line: 17)
beautytips_manager_page_attachments(Array) (Line: 297)
Drupal\Core\Render\MainContent\HtmlRenderer->invokePageAttachmentHooks(Array) (Line: 273)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object, Object) (Line: 117)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object, Object) (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object, 'kernel.view', Object) (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch('kernel.view', Object) (Line: 149)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 64)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 207)
Drupal\page_cache\StackMiddleware\PageCache->fetch(Object, 1, 1) (Line: 121)
Drupal\page_cache\StackMiddleware\PageCache->lookup(Object, 1, 1) (Line: 75)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 50)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 656)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)