just did total 8 flights today first 5 where hover only no issues. the last 3 flights were flown 15000ft to 21000ft before landing and that's when the issues shown up. on the last three flights 2 of them seemed normal no issues battery voltage readings were normal. on the third notice a issue where flight time was a little short than normal when going to land voltage dropped from 29 percent to 16 percent from 398 ft agl to land and motor shut down on ground. st16e indicated battery rebound to 40 percent shortly after. after removing the third battery noticed left side had some plastic residue on the connector head. checked the other batteries and found out 2 h3 batteries used before the last battery flown had heads melt and warped a bit. they were not warped or melted before those flights. checked the inside of the h520e and found plastic residue on the left hand side of the connector.