Even though it's a hardware problem, several of us were able to resolve this slow transfer issue (to internal memory) that you're experiencing.
However, in 'my' case, it appears to be merely a temporary resolution as I just now noticed that the issue has returned. Nevertheless, the fix increased my transfer speed adequately enough (~ 3 MB/sec) such that I was able to load up my internal memory with favorite high res music in a number of hours.
If your internal mem currently has less than ~ 10 GB free space, I'd suggest just leaving the ponoplayer be. But, if more than half of the 64GB is still available, you may wish to try the procedure here:
https://www.ponomusic.com/0D51500002JCNSM.
