Unable to amend titles when using Photos for Mac

Following repair, Big Sur was re-installed on my intel Imac. My usual practice after importing a batch of photos has been to rename them. I would select some photos of a particular location, click on the info button and type in a new title. I tried to do this today for the first time since the iMac came back from repair, but it proved impossible. After typing a couple of letters, the cursor disappears and the iMac makes protesting noises. The problem is not confined to a particular view or mode in Photos for Mac. Whilst the iMac was at repair I used my iPad Pro to edit photos without any problem. Does anybody have an idea why this is occurring?