Is there any particular reason that made you move to the v3 router? If not, put the v2 one back in service. Each version of these routers have different issues, and if you have one working that meets all your needs, just leave it alone.
That being said, have you checked the setting on the v3 to see if it's in failover? Also, are there any protocol bindings? Have you entered the correct amount of bandwidth for each LAN? This affects the load balancing quite a bit.
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