Aug 2018 build M3LR, now at 19,100 miles. Mine started out strong & stayed at 310-311 miles range all the way out to about 12,000 miles. From 12,000 to abt 16,000 miles it steadily lost range to about 293-294. From 16K - 19K it has crept back up to 301-302. No explanation. Consistent (slow)...