You will find that the dogs go through the stage of learning everything you throw at them, then ONE DAY it all seems to go wrong and you think, "Fck what happened there then"
Dont be disapointed, the dog is becoming more confident, stick to your normal trainning programme, dont change it, remain calm when he becomes stuborn, dont raise your voice no matter how much you want to.
It will pass, but someone has mentioned already, you need to explain what the dog is actually doing.
Sometimes IT can be the owner at fault, and im not saying you are.