EU868 channel mask ack message

Are you using Helium hosted Console or running your own open source Console? Nova
If you are on Helium hosted Console, which url are you currently on? https://console-vip.helium.com/
If you are experiencing bugs in Helium hosted Console, please specify your Organization name and Device ID (ex. 3483050b-284d-47e2-8eda-e087fc03a753).

8bd91ec2-bee2-4d26-8848-d5edd221f225

Please describe your issue:

Several of my devices (with ADR enabled) are stuck in a loop whereby console sends a downlink after every uplink because my devices do not send a channel mask ack.

I can see the following in the downlink, channel mask is set to 255

category    "downlink"
data    
devaddr "64080048"
fcnt    21
hotspot {…}
integration {…}
mac 
0   
channel_mask    255
channel_mask_control    0
command "link_adr_req"
data_rate   5
number_of_transmissions 0
tx_power

And I get the following in the next uplink

category    "uplink"
data    
dc  {…}
devaddr "64080048"
fcnt    40
hold_time   0
hotspot {…}
mac 
0   
channel_mask_ack    0
command "link_adr_ans"
data_rate_ack   1
power_ack 1

I'm in EU868 if that makes any difference. Device downlinks are received, and the ack for data_rate & power get sent OK every time

helium / console

EU868 channel mask ack message #1250