[Roundcube] Elastic theme, mobile version: on mobile devices the contacts aren't displayed when using INBOX prefix

Hi, I'm using CentOS 7.5 with:
roundcubemail-1.4-66.1.el7.kolab_16.noarch
roundcubemail-skin-elastic-1.4-66.1.el7.kolab_16.noarch
roundcubemail-plugin-kolab_addressbook-skin-elastic-3.4-47.1.el7.kolab_16.noarch

The IMAP server is Dovecot with the following inbox namespace configuration:

namespace inbox {
   separator = .
   prefix = INBOX.
   inbox = yes
   type = private
   [...]
}

Reproduced on Android (Chrome 69.0) and iOS 12 (Safari). When accessing 
Contacts on the mobile device, no contacts are displayed, it's like 
there aren't any contacts. Roundcube displays:
"This list is empty. Use the Create button to add a new record."
However, when searching for contacts all the expected results are 
returned, upon selection I can see all the contact properties, so it 
appears the issue is only with displaying the contacts.
In the desktop skin the contacts groups as displayed in the "Groups" 
window appear like this:

Global Address Book
INBOX
   Contacts
     Clients
     Family
     Lists
     My collected addresses
     Other
     Providers
     [...]

Could this problem be caused by using INBOX prefix?

-- 
Adi Pircalabu