We could summon the shadow proclamation to rule on reverse loops, but run the risk of a judgment that they rightly be subtracted from your total in accordance with all that is good and proper. Total milage is pretty solid; Strava does not appear to change the value (unless you crop a ride) and in normal usage rides would never be deleted from fs.org so I can personally, but with all respect and no intended slight, insult nor vituperation, only suggest human error. That is to say, I ran a full resync on your data and the sum remained the same.
mysql> select sum(distance) from rides where athlete_id = 19607766 ;
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| sum(distance) |
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| 2619.2199988365173 |
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1 row in set (0.00 sec)