I'm seeing a couple of issues. Configuration is WAN connected to one modem (ISP1) and WAN/LAN1 defined as WAN and connected to a different modem (ISP2), WAN defined as 200k up, 20k down (yes it's really like that), and WAN1 defined as 20k up, 600k down (CATV, internet only). Load balancing options all off, Link Backup set to WAN1 primary, WAN used when all primary networks fail. All settings except those and address reservations are set as defaults.

1. I was seeing significant traffic on WAN even though WAN1 did not have any failures. As I'm interpreting the settings, there should be no traffic on WAN until/unless WAN1 fails. A typical symptom of this is web page loads stalling or downloads running slowly from certain clients (clearly going over ISP1), despite Speedtest showing plenty of unused throughput.

2. Previously I had those two networks swapped, wiring and settings, so that the ISP2 was on WAN and ISP1 was on WAN1. With no load balancing and WAN set as primary with WAN1 as fallback, the router was still sending all of the traffic (or most of it) over WAN1.

I've had to disconnect WAN in the settings to get the expected behavior, but this means we don't have at least the link fallover we wanted.

Any ideas?