I get that same thing, if I do a session with lots of pulling and direct biceps work. Just like you said, sometimes it gets so bad that I can't bend my arms at all without them cramping, except my cramps are in my biceps. It's just because I don't do a lot of direct biceps work. I don't worry about it, I just drink lots of water, get some bananas in me and drive on.
I think it's more of an indication of doing a different type of training, as opposed to exposing a weakness. My biceps are quite strong, I just don't hit them like that to often.
Current PRs at 242, raw w/ wraps- 525, 355, 605, 1485
Roboro tui, perimo vester adversarius
(Build yourself, destroy your enemy)