#3 looks the least damaged. To me that means the BMS did a good job balancing the charging, and the whole thing was overcharged. IMHO that means there was not a single defective cell. 7 defective cells? Possible but I think #3 just got lucky.
7 bad cells is possible. If they are, at least Yuasa is consistent.
I think Boeing has their work cut out for them. I think the problem is systemic, and the only way to recreate the problem is to..........fly them and instrument the heck out the charging/BMS/batteries.