Occasionally, and lately more frequently, my computer gets locked in selection mode.
Mouse wheel does not function as usual, and when I click, selection gets extended.
My system is a Lenovo Thinkpad laptop, and I am using an External keyboard, connected via USB.
External keyboard is very old and does not have the Windows KEY.
Researching about this problem I came to an hypothesis, related to mouse ClickLock option inadvertently being set, but this was not my case.
(mouse clicklock can be accessed via mouse settings/additional mouse options).
When it happens, this strange behavior occurs in any software that I am using, and my solution was to reboot.
Today I found that pressing CTRL+LEFTSHIFT+RIGHTSHIFT on my external keyboard, selection mode gets back to normal.