I run into that too sometimes, but I've never found a way to fix it when it does it, sometimes I just copy and paste the first half part and then come back to the original and select and copy the rest of it.
I have the same problem on my tablet with Android.
It's not like that. It's really hard to select anything accurately. It's like it bounces and pops around very difficult to select anything. sometimes it refuses to select anything at all. Really weird.
Try going to mouse settings and changing the double click speed down a little, try changing some options like pointer precision etc, to the opposite of what ever they are set at and see if it makes any difference.
I don't really know what could cause this except the way the mouse is working.
Does it do this in all locations and like your browser and open documents?
You know I was thinking the same thing that the mouse is too sensitive. I have another program that I use to select a picture or whatever and I'm having the same problem there selecting things. When I try to trace out the area it pops prematurely. I'll have to look to find out where the mouse setting are and try to adjust them. Thanks for the suggestion, I'll let you know how it turns out.
Yes that does seem to improve the selection of data. Thanks for your help. But another problem seems to be when I click to check a box. Sometimes I have to repeat the action several times to get it to take.
If you have another mouse try it and see if it makes a difference, also do you use a wireless mouse, I'm had problems with them, I'm a graphic artist and gave up and stuck with a wired mouse. With me it's like I get interference sometimes.
Also, my mouse has its own settings and what have you independent of the setting in Windows control panel.