We now have the siding guy in. He originally thought that it was just a problem with bad flashing.
Wrong. It turns out that the folks who built our house did not put any house wrap over the wood on this section of the house. The house wrap has now been installed and the siding will go back up tomorrow.
I am less than happy with our builder for this, but since 24 years have passed, there's not much to do about it...
This ceiling leak is being annoyingly expensive.