That sounds crazy (specifying a WAN1 IP as gateway on a static route forced through WAN2) but nothing surprises me about this device any more...

My observations on the 'single WAN' variant of this issue were that the reply packets from the alias IP back to the gateway IP were being sent with incorrect source IP IPs. No policy routing would correct it.

Making one last comment about the underlying issue. I do have a support case open about this (that case provided the idea behind the workaround), and I have been informed that they duplicated the issue and escalated the issue to be fixed. That however was in 3.8.8.2/3.8.8.3 days, the issue was not fixed in an early 2862 3.9.0 beta I was sent a few months ago, and was not fixed in the recent 3.9.0 consumer release. I last chased the escalation about two months ago and was told they'd enquire internally to see how the fix was progressing. I've not heard anything back....

Interestingly enough you can set the interface to WAN1 or WAN2 on the static route and both correct the issue zone I'm not totally sure which it should be.

I have a firewall in between the draytek and my LAN's which is transparent bridge, no routing or nat, just a firewall.

When I was observing its logs I too noticed the wrong source IP address but that went away for devices going out on WAN1 after your work around any other ideas about resolving dual WAN without static routes or which interface I should really select WAN1 or WAN2 on that route..