The downlink you’re getting is the confirmation of the uplink, just like your code requested:
Indeed, requesting a confirmation for each uplink is not good. I’d guess that changing the 1 to a 0 would do the trick to disable it.
Note that TTN Console also tells you that the device sent a “confirmed uplink”. And that your device did not receive all the confirmations, making it repeat the previous uplink, like with the very same frame counter value of 21:
Clicking an uplink or downlink in TTN Console often reveal more details.
(Aside: please see How do I format my forum post? [HowTo] Thanks.)