I have done some further investigation it appears this also wasn't working on AEM 6.4.6 so it's unlikely related to the hotfix in 6.4.8.0

Just seen this hotfix in 6.4.8.0 AEM assets - Renaming a file using some unsupported special characters like ampersand (&) creates an invalid folder. NPR-29196: Hotfix for CQ-4265037 - might this have something to do with the cause?

ISSUEI have encountered an issue where AEM 6.4.8.0 freezes and becomes unresponsive when adding a component into the data sly resource below:  <sly data-sly-resource="${'q&a-parsys' @ resourceType='wcm/foundation/components/parsys', decorationTagName='div'}"></sly>   I have narrowed down the cause t...