Photos App crashes every time I try to migrate my photos from iPhoto

Have you tried the iPhoto Library First Aid Tools on your Library?

If you don't have a current backup, make a backup of your iPhoto Library and then run the iPhoto Library First Aid Tools to repair the permissions and to repair the database.

• To repair hold down the alt/option and the command key simultaneously while double clicking the iPhoto application in the Applications folder to launch the iPhotos Library First aid tools. Hold down both keys firmly and long enough, until the First Aid panel will appear.
• The select "Repair database". Repeat with "repair Permissions".
• If it still does not suffice, repeat with "Rebuild Library".

If it still does not work, download our Swiss-Army.Knife for library emergencies: Fat Cat Software – iPhoto Library Manager

The free trial option will let you rebuild the iPhoto Library.

Then try to migrate the rebuilt library to photos.

You do have enough free storage on the disk with the iPhoto Library? Migrating needs temporarily additional storage.

Thank you! I had to resort to Fat Cat but I finally got it to work.

That cat has saved many libraries, when all else failed! 🙂