Has no news on this, sadly :(
Generally reports with lower vote count are not prioritized very high internally — and this one is sub 10 even.
Sorry, I can’t do anything to change it. Voting is the only way we can influence this.

The only workaround is still to covert a live line to a path with Object > Shape > Expand Shape before cutting and converting it back after.

Please can you update on this as it still does it. Basically when resizing a line which has been cut using the scissors as soon as you grab its left handle, the left handle jumps way to the right, sometimes even off the visible screen if the line being dealt with is quite long. It's very annoying as you then have to let go of it, scroll to the right and then hunt for where it's ended up...

Richard, does it look like this to you?
This a definitely a bug then!
The middle dot the live line has in the middle stays in place when a line is cut, while it should be repositioned in the middle of the cut segment. I assume Illustrator steal treats the new live line as if it has the same bounds, and when you scale the segments it gets treated as if you scaled the whole original path ...but with the gap on the left.
How bizzarre!

Thank you for you patience with this.
A workaround would be to expand the live shape first and scale the line as an ordinary path — Object > Shape > Expand Shape.

Egor,

Here is a file replicating the bug. The top line I cut approx half way along then the hollow selection arrow was picked and as soon as I shift-clicked the left hand handles for the right hand half of the line it jumped to the right (and shrunk) to the position shown.

If it behaves the same on your system it should do the same for you with the bottom line.

Hello Egor,
I can't put any recording apps onto my work PC so hopefully these screen caps will demonstrate what's going on.

So I have a line going all the way across the screen which I am going to cut at approx 6500 with the scissors tool, see file 1

So I cut it, and the section from 6500 towards the right comes into focus on the guides, but I can't do anything yet as the cursor is still a cross for the scissors, see file 2.

So now I select the selection tool (hollow arrow) and the line becomes clickable, see file 3.

Now I shift click the middle of the three dots, so that I can move the left end of the cut line either left or right, and lo an behold the left end of the line and the three dots shoot off to the right to approx 6630 before I even drag it anywhere, see file 4. This is even more annoying with a really long line as it often shoots right off the screen- at least with this example I can see where it's gone.

Richard, I can’t really reproduce it.
As I understand it, you mean Scissors tool selects one of the points created only, and not the cut piece as a whole, right? And when you try to resize the resulting path (with bounding box’s handles), Ai scales only the point?

It does not happen for me. When I switch from the Scissors to Selection tool, the partial selection stays, but the transformation applies to the whole path. If I do this with something like Free Transform tool or Scale tool — yes, there is a differences, both behave in their own ways: Free Transform scales only this one point (both its handles and coordinates using an opposite corner as a pivot), Scale transforms only its handles basically. But you mean just using the bounding box frame’s markers, right?

So... a video or a GIF is needed. Use something like Sharex or GifCam or LICEcap to record one.