I have 1 modification for you get a frame so you can put the cells in compression. They need 300kg of pressure from the ouside to stabilize and prevent swelling and premature delamination i dont think your build achieved that.

https://batteryfinds.com/should-i-make-lifepo4-battery-compression/#:~:text=LiFePO4%20battery%20compression%20refers%20to,delaminating%20and%20causing%20irreversible%20damage.