RN2483 don't receive acknowledged in every uplinks

Hi,
I’m using RN2483 and if server don’t have data to send to node i don’t have problems, because i receive everytime mac_tc_ok, but if i send a confirmed message from server to my node, i received the rx data and rn2483 don’t send mac_tx_ok. Sometimes works, but not everytime. What i lack?

This helps to debug?

mType:“ConfirmedDataUp”
major:“LoRaWANR1”
devAddr:“06d19f90”
adr:true
adrAckReq:false
ack:false
fPending:false
classB:false
fCnt:0
fOpts:null
fPort:10
bytes:“YnTOrBsN”
mic:“81bab7b6”

Could be some protection for replay attacks??