Text cursor jumps to other place at times

[Moltke]

In browser, text documents, writer, in everything were you can enter text. Happens completely at random, sometimes notting and other times i am more busy correcting the text due to the jumping cursor then anything else.

Oh well that's annoying indeed...While googling on  touch/trackpad issues on Linux, I found that several ones have been reported on this matter under Ubuntu 18.04 which is the one LL 4.2 is based upon. I found this article https://sangams.com.np/fix-ubuntu-18-4-t...-properly/ and I don't know if it will help you resolving your issue but it might worth trying. 

Hope this helps!