It appears in NFA 9.1.2 and earlier that the Data Retention for 1 minute Reaper data was set to only retain '86400' seconds worth of data or 24 hours.
This by default should be set to 30 days or 2592000 seconds.
The query below on the Harvester will fix this:
mysql -P3308 data_retention
update datastores set max threshold='2592000' where name ='RPA';
You should recycle the CA NFA Data Retention service after doing this.
Note that this is fixed in NFA 9.1.3