On Joomla 4.3.x, after installing the latest ACYM 8.7.4, I've noticed that all installed templates and existing emails were simply wiped out.
The extension was installed as if it were brand new.
Haven't seen this kind of behaviour since the long forgotten days of Joomla 1.0.
Moreover, when I imported a template generated on ACYM 8.7.3, the custom blocks that I have written were completely altered (with a slightly different structure and CSS class names).