I've had this issue with various builds. Currently using the latest 6.82.
It's hard to describe, so I tried to show it in these two clips: https://youtu.be/snUFOThzv60
First clip shows, when entries are selected and moved to the top of the download list, they don't start downloading right away. Which of the selected actually starts to download first, is totally random. At first I thought it maybe had to do with, which one is selected first. But it doesn't have any influence, since I clicked and dragged top to bottom and vice versa.
Second clip shows how it's pretty much impossible to select items in the download list, when it's downloading smaller files (images for example) and moving. The selection always jumps back to the top entry (selecting others as well) and depending how you select them (shift + click for example), you sometimes select the whole list. Or, when scrolled down, the last entry will automatically be selected.
Behaviour doesn't seem problematic? It is, when you want to select and delete stuff. Because then you randomly select files, you might not want to delete. All you can do is pause the download, select and delete, then unpause.
Maybe this is a Windows problem. I dunno. Maybe you can do something about it, maybe you don't. At least it's getting on my nerves. Thanks for loking into it.