Created attachment 183372 [details]
Video showin the selection problem in Calc.

I tried this in my Windows 10 laptop.
In Calc, enter some value in a cell.
Click on the cell, and go to the cell-editing area at the top.
Try to select a sub-string by clicking on left-button and pad,
(my moving a bit faster, or in an angle, I don't know).
Many times it shows a stop symbol, but not always.
But if you manage to select a sub-string by letting go of the left-button,
 then editing over it by typing new value does not end up replacing the selected sub-string.

Example:
Enter:   1234567
Now in cell editing area, try to highlight 345 by dragging the mouse over 345.
When it shows a stop symbol, manage to highlight some text by letting go of left button, and
now type 999 to replace 345.
Press Enter.
Resulting value expected in 1299967
But it shows up as: 1237645677  or some such, depending on what really gets highlighted in the effort.