The database structure was changed to UTF8-Multibyte using the Admin Tools Joomla plugin on the basis of below suggestion from the Admin Tools app..:
Things to know before changing the database collation
Joomla! is designed to work with the UTF-8 collation. However this collation does not allow you to use Emoji and other multibyte characters such as certain Traditional Chinese glyphs, Cherokee etc. In this case you need to change the collation to “UTF-8 Multibyte”. You may need to repeat that after installing or upgrading extensions. After changing the collation you are strongly advised to use the Repair & Optimise feature.
Is this not advised by you for CB?