Can helps suggest what else can be done for those devices that are not showing metrics?
UIM 20.1
SNMPCollector 4.03
Run the below query:-
update s_qos_data set ci_metric_id = NULL where probe = 'cdm' and qos = 'QOS_DISK_USAGE_PERC'
Keep in mind - You need to restart data_engine probe after this sql.