Linux pastes clipboard at "random" times

I'll be editing files, actively using a keyboard and sometimes a mouse, especially to switch windows and such. My programs open under edit suddenly have syntax errors which, ultimately come from things pasted into from my clipboard into the editor. This happens in every normal editor, not so much Gvim (mostly due to the unorthodox keyboard sequences). My mouse has a scroll wheel. The scroll wheel can be clicked like a button It has 2 main left and right buttons It also has 2 buttons on the left labeled + and -, both of which I almost never press. I rarely, if ever, press down on the scroll wheel but do scroll active windows with it. What should I look for? This is an OTB Debian installation

$ set |grep DESKTOP
CHROME_DESKTOP=code-url-handler.desktop
DESKTOP_SESSION=mate
MATE_DESKTOP_SESSION_ID=this-is-deprecated
ORIGINAL_XDG_CURRENT_DESKTOP=MATE
XDG_CURRENT_DESKTOP=MATE
XDG_SESSION_DESKTOP=mate

$ cat /etc/*release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=22.04
DISTRIB_CODENAME=jammy
DISTRIB_DESCRIPTION="Ubuntu 22.04.1 LTS"
PRETTY_NAME="Ubuntu 22.04.1 LTS"
NAME="Ubuntu"
VERSION_ID="22.04"
VERSION="22.04.1 LTS (Jammy Jellyfish)"
VERSION_CODENAME=jammy
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/ "
SUPPORT_URL="https://help.ubuntu.com/ "
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/ "
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy "
UBUNTU_CODENAME=jammy