Short circuit! Replace the spring, not sure where to get them but google can probably help. I'd be really careful using the battery again, if it doesn't look or smell damaged, charge it and keep an eye on its discharge with a multimeter. Some may recommend disposing of it and using a different one.
Make sure you are very careful about preventing shorts in the future, and check your resistance often if you aren't sure about a particular rebuild. I assume you are using some kind of RBA.
P.s. My troll detector is blipping at this one, but I'll give you the benefit of the doubt for now.
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