Last night I was watching the CNN show on the lost Triplets using the C61K when suddenly at 8pm it went to record a 4K show that i had setup a schedule for. I was surprised when it suddenly switched channels on me. It seems like it cannot record a 4K show while you watch another show? Honestly I did not try anything because I was in the middle of an important scene in the show so I switched to the HR54 and when that powered on the picture had no audio and the video kept disappearing for a few seconds, so I switched to the HR24 and that worked fine. Later on I tried recording a 4K show again, this time with the HR54 on before starting and everything worked fine on the HR54. Very odd that it was breaking up when switched on in the middle of a 4K recording!