Merge dialog doesn't show values of multivalue custom fields

I merge two contacts. If they have different values in custom multivalue fields, these are not displayed.

The contacts have a custom field that allows to check multiple values (screenshots contact1.png and contact2.png). As you can see in the screenshots, the contacts have different values checked in their custom fields.

• I navigate to Administer > Manage > Find and merge duplicate contacts
• I use a rule (e.g. Individual strict) for searching and search on all contacts
• In the list of merge candidates, I click on merge and get displayed two duplicate contacts (screenshot merge.png)

In the merge dialog I expect to get all checked values of the custom displayed. Instead

• the field of the left contact is completely omitted (the user will think that the user has no custom data)
• the field of the right contact is shown as "Array"