I suggest the first step is to
run WeeWX directly to see exactly what is being included in the archive records. When run directly WeeWX will display loop packets (LOOP:) and archive records (REC:) to the console.
rxCheckPrecent will (should) appear in archive records only. Let WeeWX run for at least a couple of archive periods to ensure you see at least one archive record and then post the entire console output here.
Gary