This seems to indicate that Wowza had problems reading a particular file. It could be corrupt and you can easily test that by copying it to your Wowza content dir and streaming it via a vod app. It could also indicate a problem with the file in Mediacache. I would certainly ensure that your Mediacache setup is optimal and you have enough capacity both in terms of disk IO and network throughput. If your platform is tuned and this is happening consistently then you may want to
open a support ticket. If so, please include the detail requested and we will investigate it in more detail.