Evolve ESC & 10s4p Power Issue

I figured I should ask about this ESC issue here, because my friends Evolve ESC is not powering on atm after I used a part from it to test my own faulty ESC. I intend to replace it but I am concerned about the cause of this power issue, in case I might accidentally replicate it.

His ESC is in question because after my friend had lent the top half of it to me to test my own ESC that was having power issues, it will no longer power on after reconnecting it back to his ESC again. My own ESC issue was due to the faulty bottom-half of the Evolve ESC; it was causing my motors to stutter, so I used my friends’ ESC top half to see if the problem persisted. I suspect this caused his top half to become faulty somehow.

However, I also suspect that maybe my battery is the cause of this power issue because, long story short, several really bad spot welds over double 0.15mm nickel strips drove me to remove all strips & change the setup to a single strip spot weld instead; I had disassembled the pack several times to address multiple spot weld issues. But even so, I feel that the ESC should at least power on despite this decision.

I hesitate to go any further due to these sudden extra costs to my 10s4p project; would anyone be able to provide some insight into this mess & help me ID the cause of this power issue?