When you destroy block where there is item frame on it, it takes from 10 seconds to up to 30 seconds to pop out itself. I don't remember this happening in 1.6 but I am not sure either. I don't think it's and huge priority to fix this, but it would nonetheless be good to do so in my opinion.
If this is an duplicate, I apogolize, but I could not find anything along the lines of this elsewhere.