I've had this on several occasions recently. Also skipping and jumping of live and recorded items. I was worried my hard drive was failing until I looked further into network connections. Often when this has been happening it's while the Tivo is in the process of connecting to the network. When it's happened on recordings if I look at the last connection it's often at the time the recording took place.
Very frustrating
it's only been the last few weeks. I also note that my Tivo is now connecting about every 5-6 hours instead of just one or twice a day. This new schedule means with the amount I record it's likely to happen a lot
I'm tempted to swap the two boxes around to see if the other box is better. This one has been used far more, but I have several series on it I haven't worked through so really don't want to trade it for a new one if it can be avoided