I don’t have this issue with Libre Office but I have similar issues with Adobe application cursors not behaving as they should if I have windows scaling options too high or too low for that application. I use large 4k screens and sit a good 3 meters from them so I need to increase text scaling otherwise text and other things are microscopic and can’t be read or they don’t display correctly. Try turning your operating system scaling options up or down, test that out.
I have to use weird numbers on some of my screens so everything is legible and works right.
There isn’t a whole lot of content for 4k technology and the technology it self hasn’t been mastered yet. Most applications, movies, and games are not designed to run in 4k resolutions and scaling. For that reason it really doesn’t provide any benefit, more issues than anything, to use 4k settings. I work with multiple applications and coding often. It’s useful for me to be able to have as many windows visible and accessible on one screen as possible. I don’t use 4k settings because the scaling is screwy and it makes cursors behave weird like you’ve described.
It’s scaling because the app, and many apps, are not designed for the resolution you’re using. If scaling doesn’t work you’ll have to resort to using a larger scaled resolution, not a 4k resolution, as I did because I had to because of the same kind of issues.