We recently started experiencing this error with collector when we have multiple users editing the feature service occasionally. Sometimes the retry will work and sometimes it does not. Has anyone experienced this in collector we have tried several workarounds but none seem to resolve this from coming up. We have consultants working with a feature service via collector and ArcGIS desktop so it we do have more editors than usual. Some options I am considering is using a named version which I would prefer not to and I'm not sure it will have any different results. We also are running ArcGIS server 10.1 and this may be related to a bug. If anyone has any insight it would really helpful.