I've had many issues in the past adding boarding passes on flights ex-AMS to the Apple Wallet before, even DL operated. In the end I just went with paper because I didn't trust the technology. I've also had issues with seat maps on DL flights ex-AMS starting at about T-24 to T-48. I believe all of this has something to do with the interface between the KL and DL systems, as even DL flights use KL systems for departure control in AMS.