All,
https://www.logikalsolutions.com/wordpress/wp-content/uploads/2022/11/qfontengine-issue.png
I "think" this one is yours and I "think" it might be related to deletions and disconnects across threads/event loops getting queued. To recreate you need to have two different paths to get to the same method launching a QPringPreviewDialog. Go down one, view the dialog, close it, then immediately open another print preview. Somewhere between the second and fifth invoke, you crash with a double free error.
I didn't dig into the QFontEngineFT code to see if there is some "shared" resource that would get a queued deletion with the destruction of the dialog, but it feels like it.
QPrintPreviewDialog issue
Re: QPrintPreviewDialog issue
We have this on our to do list.