Encountered it today, for BMP too, on 3.2.2
We had a severe trouble as we used a CMP to store the state of a BMP bean. As it appeared, the double ejbStore is a recursive call and for some reason, something triggered a sync, which triggered more ejbStore, which in turn ... which lead to StackOverflow and OutOfMemory exceptions.
So, as a temporary fix, we added a boolean variable to ensure that if our BMP was already in ejbStore, the recursive call would end immediately. But this is a hack and any explanation on that double ejbStore behaviour will be welcome.