Comment 2 for bug 1902643

Thank you for taking the time to file a bug report.

Can you provide more details about the issue? By "copy paste mode" I assume you're referring to the copy mode you enter when you type CTRL+b [, is this correct? I've made an experiment here and left tmux in this mode for several minutes, and nothing happened. I'm thinking that maybe there is some other component influencing/causing this behaviour. For example, are you using some terminal application (like mate-terminal, gnome-terminal, xterm, etc.)? If yes, are you using its default configuration? Also, could you share your tmux configuration?

I happen to use tmux in my Focal machine as well, and I have never experienced this problem.

Since there is not enough information in your report to begin triage or to
differentiate between a local configuration problem and a bug in Ubuntu, I
am marking this bug as "Incomplete". We would be grateful if you would:
provide a more complete description of the problem, explain why you
believe this is a bug in Ubuntu rather than a problem specific to your
system, and then change the bug status back to "New".

For local configuration issues, you can find assistance here:
http://www.ubuntu.com/support/community