Just received this email from Renault ...
I would like to thank you for confirming the VIN for your Renault Kadjar. With this information, I can see that the Renault Kadjar was manufactured in 2016. During this period certain R-Link 2 experienced the issue you are reporting. This at the time was reported to our technical team. The investigation found that the DAB signal loss issue is caused by the high electro-magnetic noise inside the radio that disturbs the DAB radio reception. This problem was corrected later on with a new "Hardware Innovation" series. This correction was introduced to later models of the Renault Kadjar.
With this in mind, I am sorry to say that there is no hardware o software that can resolve this for your device. In the meantime I will now close this case, however if you have any additional questions please do not hesitate to contact me by e-mail or by calling me on the number below and I will gladly open this case for you.