why does the BL072Z loses some downlinks from TTN?

[jg_spitfire]

Hi, is there any reason why the BL072Z node sometimes loses downlinks?, I am using a single channel gateway working in the 868.1MHz frequency and I have modified the three default channels of the BL072Z node to this frequency, in the uplinks I have no issues but in the downlinks yes, does anybody knows why?

thanks