i've suffered with this!! didn't put a hole in it but ground it away nicely!
had mine replaced with a beefier one machined from billet alu! no probs since!
just keep an eye on it.
2 mates have had the same, changed to the beefier billet version and all ok now! (one did hole his, but i saw him deck the plug out and told him to stop. Which was a good job as it spilled its guts right there within about 2 minutes!
)
Will find out the possibilty of my mate getting some machined, he may punt a few on if anyone is interested. I will get a pic of one.