This is what happened to me... There is a drain from the bottom of the freezer to a tray underneath. When the freezer defrosts, the melting water drains out of the freezer into the tray, where it evaporates. The little drain hose got plugged up so the defrost water just pooled up in the bottom and refroze until the ice level got too high, and it leaked out.
I cleaned out the drain hose, and it worked fine after that. You may need to take the panel off that covers the cooling bits to get to the drain, I had to.
It took me a while to figure out. First I thought it was the in-door water dispenser, then the icemaker.