I remember seeing your other thread when your were concerned about the carers their and what they said.......
What you are saying is completely and utterly normal. Remember as much as you said he is happy he has had a bit of change in recent times and kids can 'react out' because of it.
I would try not to get worked up about it. Give him time. It took my 3 year a good 5 months to be completely settled at his new daycare.
My son was biting, hitting the works. Now I never hear any kind of reports like that at all.
Just keep working with the carers and reinforcing what they do at home. The great thing is that they are supportive and willing to help.