dvr recordings have sound glitches

My DVR recordings that are older than 3-5 weeks have suddenly developed sound glitches.  Nothing wrong with the video, but sound goes silent for a few seconds on my TV.  When I try to play back the same recording on my computer I get bizarre sounds like a broken record where the blank sound on the TV was.  There is no problem with live TV, nor is there any problem with newly recorded shows.  Also, prior to 3-5 weeks ago all my old recordings played back fine.  We tried re-booting the modem with no luck.  Since the live TV and recent recordings are both ok and since the playback problem exists on BOTH my TV and my computer, my guess is that some event happened on the Xfinity cloud servers to damage all those files.  Any suggestions or are all my recordings now toast?  Thanks!