On a router with multiple IPs (either v4 or v6) the kernel may often pick a non desirable source address.
In my case it often picks IPv6 addresses that are not routed to the external world, thus breaking connectivity.
I must resort to using any source-address argument that may be available for the tool I am using.
However, tools may not always have such argument and also always doing so can be quite cumbersome.

A workaround is to mark a certain IP with the 'home' attribute (i.e. via iproute2).
It would be nice if such attribute could be configurable through VyOS as well.