If you don`t find a solution for wakelock problem then it`s probably USB/charging port.
I had same issue 1 year ago and then it was issued by Audiomanager app and after that few weeks ago. I thought it was some app again but it wasn`t, it was faulty USB port.
As I understand this is not something strange for this device as many people experienced the same problem. Bought the replacement from ebay and now everything works fine.
I also had half-working USB cable from beggining, PC connection constantly reconnecting and I figured it out it was cable problem year and a half after I bought it, never thought to try another USB cable
Just a little frustrated with Samsung quality. The only thing I like about it is how easily you can replace everyting inside. I went a little OT