RAK7249 GPS not updating TTN v3

Issue:
The GPS information is not received properly by TTN (no update on location)

Setup:
RAK7249 with latest firmware (1.3.6_RAK b150)

LoRa® Server: TTN v3 (The Things Stack Community Edition)

Details:
The coordinates are displayed in the LuCi Interface correctly.
However, the coordinates are somehow not sent to TTN v3.
This functionality is needed by our client to help tracking assets.