Yes, when a connection which is participating in load balancing comes up it will cause established sessions to be reset. This is due to the requirement to update the routing table and provide those sessions with the best possible route out the EdgeXOS appliance. This only happens when a connection comes up, and thus should not occur very often and not during normal activity.
If a customers circuit is bouncing there are steps that can be taken to prevent this from happening as often, including increasing the link control settings or setting the specific link to be nailed up, however if a link is bouncing that is typically NOT a good link to use for load balancing. Perhaps it should only be used for failover as a backup link.