Im having the same issue, works ok for a few days then it starts reporting this IO error.
Im using a USB hub with external power.
After reboot it works flawlessly again

Found the issue.
SD wasnt fast enough for mumble SQLlite db
I just moved it to a ramdrive (used $mount -t tmpfs tmpfs /ramcache), and high latency was gone

Hi Im running mumble-server on a raspberry pi on my LAN network which runs raspbian. The voice channel (UDP) is working awesome with 1ms or so delay, but the Control Channel (TCP) has a really high latency as show in the picture below, as a result switching between channels take ages. Could use some...