Downlink payload Problem

I see this in my live data feed in TTN V3 console for my device:

18:03:11 Forward downlink data message FPort 1 Payload 0A12030200

However gateway actually sends this long packet (decrypted payload):

0503D2AD84060703184F84500704E85684500705B85E84500706886684500707586E84500805

Correct payload is the one from the live feed (0A12030200).
I send downlink messages to TTN server from MQTT in Node Red. Downlink packet is succesfully receieved by device, but instead of 5 bytes payload it gets 38 bytes. Though packet is decrypted without error.

I am using RPi gateway with iC880A-SPI with Semtech UDP packet forwarder. On TTN cluster V2 I had no problems with downlinks.

Can anyone please help me with this?