Trestle TinyMCE Gem Uncaught TypeError: Cannot read properties of undefined (reading 'dom')

Question

After clicking on the source-code button of the editor, the complete text vanishes.

Gem details:

gem 'trestle', '0.9.2'
gem 'trestle-auth', '0.3.0'
gem 'trestle-search', '0.4.1'
gem 'trestle-tinymce', '0.3.1'
gem 'tinymce-rails', '5.10.1'

Step 1:

Step 2: