As noted there is no relay.
We have an 11 354ts also.
Here is a pic of our "command center".
As you can see I have marked the switches, including the porch. Is yours basically the same?
I found that Coachmen installed some switching upside down (up for off, down for on). Assuming you ruled that out, it sounds like some kind of miswire going on.
On our 354 there are also small lights at the bottom of the door that are attached to the same switch. They come on when the door is opened, however, the porch switch must be on for them to come on. So to have them work and not have the porch light lit all the time, I also removed the bulb from it. Does your 354 have these foot lights at the door?
We use awning lights, so the lack of the above door porch light is not an issue for us.