[נפתר] Special characters and emojis disappear after saving a translation in the Advanced Editor

Background of the issue:
I am trying to translate from English to Dutch (both automated as well as manual translations). My database is utf8mb4_unicode_520_ci.

Symptoms:
Whenever there's a special character (like an &) or emoji in the text on the left, it disappears when I save the translation on the right.

Questions:
Why do special characters and emojis disappear after saving a translation in the Advanced Editor?
Is there an issue with my database configuration (utf8mb4_unicode_520_ci)?