eBay Order's Buyer Phone is Missing in Yaballe - Why and How to Fix It?

In eBay the buyer phone number may appear in two places:

• The buyer account details
• The phone number the buyer can choose to add during checkout. 

Yaballe API tries to get both of these source of information from eBay, however per eBay API documentation and statements:

Due to privacy policy laws for different countries, the returned information can vary.  For example, the checkout information (if available) is returned for DE/AT/CH, but the buyer account phone number will not be returned for DE.

Given the above, Yaballe API users that sell in eBay.de - will be able to see the buyer's phone number in Yaballe > Sold Items page only if the buyer added a phone number during checkout.