I have no idea what version of Qt Calibre is using but if it is Qt 6.5.x series, Qt had a large number of bugs related to Accessibility only on macOS. The issues were not fixed fully until the Qt 6.6.2 series. Many mac users have macOS Accessibility tools installed like VoiceOver, and Rectangle, and etc. This causes lots of segfaults on macOS just navigating lists, tables, and things. We (Sigil) finally moved to Qt 6.6.2 just to get all the fixes. Sigil now uses Qt 6.7.2 and it is very stable on macOS when using or running concurrently Accessibility tools with MacOS.
See
https://bugreports.qt.io/browse/QTBUG-121008
and
https://bugreports.qt.io/browse/QTBUG-119526
as just 2 of many related Qt bug reports about crashing on macOS related to accessibility apps