Import fails on adding contacts to a group using contact ID only

Importing a file of contacts to add them to a group, using 'contact id' to pick up the contact, I get the crash shown in the attached filecrash.txt. These are all existing contacts so I cannot see any reason why this should occur. The file could not be processed because of this error so I wrote some code and did it myself. Civi release is 5.46.3 running with Drupal 7.