List focus jumps to first column after selecting multiple rows

In reply to

we are still in the process of narrowing the whole thing down, aren't we?
I run 3.01 frequently on a W8 portable installation with loads of background processes and an Intel graphics card and external USB-HDD, a wide display with 2560 pixels - no jumps.
I also have that already mentioned laptop with just 1440 pixels - no jumps.
An AMD PC with loads of HDDs and SSDs and a 1680 screen and alternatively bootable with W7 or W10 - no jumps
(They all run MP3tag.)
I know that you are annoyed - I would be. But the reproduceability is still the major problem. How should you correct something if you cannot test whether that was really the fault?