Tagging contacts (found by search) with 2 or more tags (part of parents) fails. Only last tag is considered

We have tag groups (parent tags) which have several detail tags.

parent tag: animals

detail tags: dog, cat, reptile

Selecting contacts by Find>>Find Contacts;
then use the bulk action "Tag Contacts (assign tags)" and select several tags of a parent-tag.

Confirm and only the last tag of the selected tags is used.

Please see screenshot