TM is the most catankerous & worst Backup App I've ever run accross.
Thanks for your tips.
It hadn't occurred to me that I can turn Time Machine OFF and then just do backups when I want to.
Even if you have Time Machine switched off, you can still use it to back up using the menu bar icon. Click the icon, then click Back Up Now to perform a manual backup. However, it’s best to enable Time Machine’s automatic backups. To set this up, go to Time Machine > System Preferences and switch Time Machine’s status to On. It will now automatically maintain backups of your content every hour for one day, every day for a month, and weekly beyond that.
So I'm going to turn TM off.