Lorawan 868 (asr6501) Confirmed Downlink - missing ACK

[MadsLund]

Hello
I have been struggling with the ASR6501 module and the Atom DTU for a few days.

When I send Confirmed messages (CLASS C), the first 2 get through, (CSTATUS:3) and I get ACK back to my gateway.

After the 2nd message, there is no ACK (CSTATUS:8) returned.

The device are still receiving messages, but no more ACKs returned, and CSTATUS remains 8..

Does somebody knows what to look for.
I have tried OTAA & APB, Same/different Frequence - i'am running out of test ideas ?