Hi Jim
A QOS (Quality Of Service) error in the event log means that A packet has been lost on the ACE connection. 1 or 2 of these errors occasionally is nothing to really worry about you will probably not notice anything different with the system. If you have lots of these errors regularly you should probably get this resolved and you will be noticing glitches in the audio and possible the control of the system.
The most common causes of this problem are:
Badly crimped RJ45 connectors
Damaged Ethernet cable
using a cable that has not been unwound from the reel
interference from other power sources near your ACE cable
Try using a shorter different cable to see if this resolves the issue.
Regards
Sam A&H