Unable to add related products with Greek names

-- HikaShop version -- : 2.5.0
-- Joomla version -- : 3.4.3
-- Browser(s) name and version -- : Chrome, latest

Hello,
After updating to Hikashop Business 2.5.0, there is a problem when we try to add related products, which have Greek names. The problem stands even for products that have part of their name in Greek. Only products with titles in latin characters appear in the drop-down list. All the other products are refered as [null] and, therefore, are un-recognizable and cannot be added by clicking on them.
A second issue is that through the online update screen the system sais that we already have the latest version of Hikashop Busines 2.5.0, while in your site it seems that the latest is 2.6.0.
How should I proceed with the update?
Thank you in advance.
Antonis