Problem adding titles to Mac Photos

We're not clairvoyant nor can we see you MBP so you'll have to give us a lot more info than *****.

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The usual way to add a title to a photo is to type a title into the title line of the Info panel for a photo. Is that what you have been doing?

I noticed on Big Sur that Photos is frequently unresponsive when I try to change the metadata of a photo right after importing a new photo. It is easier change titles and keywords after waiting a bit - when the photos appear in All Photos and not only in Recents or Imports.

It would help to know what happens when you try to add titles. Also where is you library located and, if on an external HD, how that drive is formatted and connected to your Mac. How big is your library? Do you have iCloud Library enabled and, if so, is "Optimize Mac Storage" also enabled.

Also, have you installed and run any "cleaning", "optimizing", "speed-up" or anti-virus apps on your Mac?