We need to know more about the situation it is in. can you describe or post a photo of its situation? I'm not convinced planting depth would bother it much. It is putting on new growth quite healthily.

Here is a picture. It is in a half shade area. I transplanted it about 2 years ago. I planted it 4" too deep so the branches are under ground now. it is not doing well, has some dead branches, etc. no fertilizer, only water and mulch in winter. I am going to replant it this weekend. But would like to know if I did something wrong.