I rarely used the radio, DAB or FM, on my car after I got it in April 2016. Whenever I tried using DAB, I found the signal very flakey and gave up on it and just used music on my USB stick.
In late May this year, when I had the climate control faulty condensor changed under warranty, the dealer also upgraded the OS after I'd requested it when the fault on the condensor was confirmed after I'd reported the problem a few weeks earlier.
The upgraded version I now have is 59.00.502 EU N. I have tried DAB far more since the upgrade and I've noticed the signal is no longer flakey and I only loose it for a few seconds when travelling between regions.
So if I were you I'd be requesting the dealer updates the OS to this latest version and, if they stall at doing it, either try another dealer if not too far away or try contacting Mazda Denmark's Customer Serice department for assistance.
Hope you can get this done and it solves the DAB problems.
2016 Sport Nav 2.0 Petrol Automatic Arctic White plus options