Well, your vid shows what's happening here as well. So it isn't Cud behaving badly

It's perhaps rather a misunderstanding of what to expect.
I suspect that xircon had a column selection and then wanted ADD another, separate column selection to that (at least that was my case). I thought (and perhaps xircon did as well) that this would work with Ctrl+Mouse drag. I may be wrong though.
At any rate, how then do I select a second column block? Imagine a file with 100 lines like this:
line00
line01
...
line98
line99
I select a column block from the "i" of line01 to the "i" of line09. Next I want to select a second column block from the "i" of line80 to the "i" of line95. How? Clicking 16 times with Ctrl held is a possibility but tedious and not good for dozens of lines.