Itunes Radio stuttering, not buffering correctly.

I have an issue with iTunes Radio that seems to have just sprung up out of nowhere. I have listened to ITunes RAdio for several months with no issues whatsoever. The last few days all stations are unplayable. Individual songs are downloading just marginally slower than the song is playing so there is a constant stuttering, stop/start of the song, it will play a few seconds, stop briefly and then start again.

- My internet connection is otherwise fine. I have a steady 1,015KB/s and good line speed whilst the problem is occurring.

- I don't believe anything has changed with my system hardware or software.

- I last updated iTunes on 18th Sept to v. 12.3, radio was working fine until around 28th/29th Sept.

- My internet connection is otherwise ok, I can stream other radio services and download just fine. I have tried streaming video whilst the problem is happening and the video streams ok but iTunes radio still stutters.

- When I first log in to my computer in the morning the radio seems to work ok for about 4-5 songs and then the problem starts and it stays like that all day until the next morning.

- I am running an iMac, Late 2013 3.2GHz, 16 GB. OSX 10.10.5. Modem connected via ethernet to Time Capsule and computer connected to Time Capsule via Wi-Fi - strong wi-fi connection

- I have restarted computer, modem and time capsule to no avail.

- Looking at iTunes when the song is playing there is a light grey bar showing the song download and a darker bar showing the song playing. The light grey bar (downloaded portion) is simply not moving along as quickly as the song is playing. If I pause the song for a minute and start it again the light grey bar has moved forward considerably and the song will play fine but eventually the play will catch up to the download and it is start and stopping again.

It seems as if there is some kind of buffering issue?

Please help before I abandon iTunes radio.

Thanks,

Darryl.