Downlink failing after join

Hi.

It seems somehow that downlink is failing after we do a join.

This does not work properly:
SEND_JOIN
Enqueue data (tx)
SEND_MSG
DONWLINK WRONG.

This works:
SEND_JOIN
SEND_MSG
Enqueue data(tx)
SEND_MSG
DOWNLIN OK

I have tested 2 servers.
Loraserver seems to fail but The thing network does not.

LoraServer:
LoraServer
Downlink should be 30313233, size its righ

TTN:
TTN
Seems to be right here.

Does anyone experimented this problem?
LoRa module RisingHF RHF76-052

Seems to be happening only after sending a message after a join.

No one has this problem?

Tried another module same issue, multitech mDOT
Sending 30313233.
First packet, size is right but payload is wrong
Second Packet, size and payload are right

at+join
Successfully joined network
OK

at+send="test"
463312de
OK

at+send="test"
30313233
OK

Seems weird, and could be a server error.

Test with TTN server reveals that Downlink is sent after several Uplinks are made. Could this be an error of LoRa-MAC implementation?

Is there anyway to tell the server “wait, don’t send this in uplink fcnt 1”?

Thanks