Because the problem (no sound, even no noise) occurred when the jacks (grounded sleeves) were mounted on the case, I started looking for continuity between circuit and case, resulting in a grounded signal once the jack connectors were installed. With a DMM I found that pin 9 of IC1 was connected somehow to the case. Only logical explanation was that it was connected to the case through the connection of potmeter P1. I increased the distance between potmeter connections and case, and the problem was solved.
The Swah is easy to use and sounds really nice on my bass. I can’t wait to select and start a next project.