Actually all DJI intelligent batteries should be deep cycled and ground tested before inflight use. All new batteries should be discharged to below 5% and fully charged until cycle is complete. (many new DJI user frequently can't wait for a battery charging cycle to finish and remove the pack from the charger before the charging cycle is completed because it was pulled mid charge the battery is not fully cycled and has greater potential to fail.) No LiPO battery can be charged without proper balancing, DJI intelligent batteries are balanced during full charging cycle, cell levels can be checked in the DJI go app before/during flight and the battery/individual cell levels are logged in the app as well so you can see exactly what failed.
Here is a link to a thread on deep cycling TB series batteries and all DJI batteries for that matter, deep cycle charge should be done before the initial charge of a new battery & every 10 flights on each battery. See Page 22 of i1 manual. (Best way to discharge your batteries is to run the unit on the ground without props on until battery level reach below 5% in the DJI app)
TB47/TB48 Deep Cycling
Please share your flight log OP
It could have been the battery was not fully cycled before initial charge and that cause it to fail on flight number 6 as you stated in the video. I personally have never seen a battery on mavic, phantom 2,3,4 or inspire series become unseated mid flight only upon crashing, the unit won't power on if the battery is not seated, post your flight log it will show exactly what happened at time of failure. Only batteries I have seen move in flight/connection loss was on blade 350qx, phantom 1 (pre-intelligent battery) and s900, s1000, and old cinestar 8 models.