I was able to find this under a 450 user manual... https://usermanual.wiki/Cambium-Networks/50450M.USERS-MANUAL-PART4/info
outdiscards Count This field displays how many outbound packets were discarded without errors that would have prevented their transmission. (Some of these packets may have been discarded to increase buffer space.)
I might start by investigating the connected AP's frame utilization, particularly on the uplink, and see if it is becoming oversaturated...