Weak link in side by side pack's?

[Sneeck]

I'm chargeing my small fleet of side by side pack's at the moment, and I just noticed that some silver bar's get warmer than the cell's itself. Now as an electrician I know resistance ~ heat, so is it possible the solder joint's on that bar are bad?

The pack's are Corally 3rd generation race spec matched gp3300's(whateverthehellthatmeans) charged on a millenium pro at 4 amp's. They got heatshrink around them.