Yes, I understand the problem, but in my opinion you should focus on the board temp primarily. Afterwards we'll look at resistance.
Plug in the 75C mod (nothing attached to the mod)
How much does the board temp rise just sitting there and not being used?
Note down temp after 2 minutes and 20 minutes after being plugged in.
Leave mod and escribe running. Attach Bakx.
How much does the board temp rise just sitting there and not being used?
Note down temp now and 20 minutes after being plugged in.
Report back those 4 temps like below , and battery description.
75C Nothing attached
2 minutes (temp here) 20 minutes (temp here)
75C bak attached
2 minutes (temp here) 20 minutes (temp here)