HR 21 issues

I have an hr21 with 1tb wd external hard drive. I have a number of shows taped and when I play them, there is pausing, hestitation or whatever you want to call it. I dont know if it is the hard drive, the unit or what.

Anyone have any suggestions on what to do? When the show keeps getting video/audio dropouts, it is hard to watch a show.

I have noticed that if I hit pause, stop for 10 seconds and then go again, it doesnt happen as bad.

Thanks

Jim