Steps to reproduce

1. Create and set up a moodle site.
2. Login as admin.
3. Go to Site administration > Course > Groups > Group custom fields.
4. Add a category and create a custom field (I created an optional checkbox).
5. Create a course.
6. Add a group.
7. Create an activity (for instance, an assignment).
8. Create a backup for the activity and download the backup file.
9. Create and set up another moodle site.
10. Create a course.
11. Restore the activity from backup file
12. The error is shown below:

Can't find data record in database table groups.

Debug info: SELECT * FROM {groups} WHERE id = ?
[array (
0 => 2,
)]
Error code: invalidrecord 

The issue is the backup file has groupcustomfield, but not group.