When I edit a title clip with "show background" enabled, the background (a video clip on another track) is displayed with a distorting horizontal stretch, making it difficult to place text elements accurately in relation to the underlying video. This happens after updating to 19.12.0, the background was fine in previous versions. Has anyone else noticed this, or even better, knows a workaround?

something like that ?

https://invent.kde.org/kde/kdenlive/issues/482

or that ?

https://invent.kde.org/kde/kdenlive/issues/311

Yes, a bit like the first one, except that there were no transform effects applied to the clip.

Just realised that this has been fixed in 19.12.1, so I'll just have to wait until OpenSUSE Tumbleweed delivers that version (should not be long, they're very quick in that respect). Thanks for pointing to the previous reports!
Edit: just installed 19.12.1 from the repos. Problem fixed, great!

nice