Why does LibreOffice calc become very unstable and unresponsive the longer it is used? Touch one cell and 2+ are highlighted.

Cannot enter new or updated information.
Program locks up and I have to save my work.
Then I have reboot my computer.

Please, read the guide. Which OS and LO-Version do you use? Which Hardware do you use? What does “longer” mean, two minutes, two hours, two days? Is your hardware okay? Check your PC system.