Space bar issue - or maybe processing issue?

SPACE BAR PROBLEM - I have a Mac Mini 2023 16 GB. A week ago, I got a new keyboard and mouse. Since then, I have had issues with the space bar - it works intermittently. I changed back to old keyboard and mouse - same issue. Each time I added the keyboard, I set it up and tested it. Then throughout the day, the space bar would stop working. When this happens, it get a blue box somewhere on the screen, like there is a pause and the computer is processing or something. The blue box might be 1 x 1 inch or it might be the entire screen. When the blue box disappears, the space bar works again. This happens in various settings - writing an email, working in an app, on google. Help.