The PDF engine is different in AC11. In my view it's better, faster and gives me more compact pdfs. I'd guess you've got some content (a library part? an included odd bit-map image) that makes it choke. Turn off layers in turn to find it. A workaround might be to
Print individual layouts to PDF. (Use Adobe PDF printer utility or the like).
AC4.1-AC26SWE; MacOS13.5.1; MP5,1+MBP16,1