Andrew,

Win7, latest stable QCAD trial release installed from ZIP file.
Version: 3.31.2.0 (3.31.2)
Build Date: Oct 27 2024
Revision: bae1b88
Qt Version: 5.13.2
Architecture: i386
Compiler: MSVC++ 14.16 (2017)

Fresh restart of QCAD loading an existing file.
-> Mouse wheel = Zoom IN/OUT

Switch to Print Preview mode (Ctrl+Shift+P)
-> Actuating the mouse wheel sets the origin at the left lower corner of the GUI view area.
-> No zooming occurs at all.
-> I can zoom and pan with other methods but actuating the mouse wheel in Pan Zoom mode exhibits the same issue.

Switch back to Model view (Close Print Preview)
-> Issues remain.

I can replicate the same behavior when starting QCAD and selecting a Layout with Viewport from the Block List. Essentially automatically in Print Preview mode.

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What seems to be fixed in the mean time (3.27.6) is that the mouse wheel = vertical scrolling after visiting the Application Preferences. Or in and after Print Preview mode.

I would upgrade to the newest release for production when I could turn off the "Show" buttons. The Always show all properties preference of the Property Editor has no influence on that. See: Related topic

Regards,
CVH