Yes you are right there does seem to be a problem with the quality of the solder.
My advice would be to use a non MB battery as they have less aggresive amps than those from the genuine article. The more aggresive amps while more effective, do lead to solder fatigue.
You may have seen the discussion @ I used to be a battery snob...
Credit to Cap'n for postulating this hitherto little known theory!