When I add notes to Contacts, the cursor loses focus on my iMac

When I add notes to Contacts, the cursor loses focus and I will be typing and start getting the "beep" that the typing is actually going nowhere (mouse/cursor lost focus). page moves I loose valuable information , Going on for 10 years, multi May OS updates. I was told that Apple no longer supports OS 12.6.7 by last apple support ticket even thong I pay for support. I had to Use agin recently and the issue is still the same.

so I have to Spend $3000.00 plus to buy a new iMac and I can't use my 27 inch 5k screen!

[Re-Titled by Moderator]