I don't know which adapter did it, but with the super tight BMC mount one of my adapters grated off 2 of my EF contacts. Luckily the iris and IS still work.
Got a note from Kristian at BM on there forum:
While the damage won't be covered under warranty, it's not going to cost a lot to fix. Once you have the downtime and want to get it sorted, contact tech support and speak to Kaspar. He'll sort you out.
You should only have to pay for shipping to and from our Fremont office in the US which won't be much.
Some one on the BM forum suggested that it might be from a "chipped" adapter and I'm sure that is what has caused it. Time to get the chip off of them.