Surgery was a success. As someone who should only be half-trusted with a soldering iron, that’s a huge relief.
Now that my patient is safe, I can tell the story:
When I bought the bass from the UK in late summer 2023, I had the store put in series/parallel toggles. Orginal Dingwall part, a store well versed in all things Dingwall - piece of cake, right? Wrong.
What I received was a beautiful rare Dingwall that had an annoying electronic buzzing in certain settings and, what’s worse and what I actually only realized recently: A middle string that was weirdly out of phase sounding and had severely lower output.
Through several mails with Dingwall Tech Support - shoutout to Davis! - we finally found out that the store didn’t only solder through the toggle board instead of using the terminals but that they had apparently switched the order of the pickups, causing this "out of phase" issue.
Dingwall lables their pickups "neck" and "bridge" on the bottom, but as there are no pickups labeled "middle", 3X basses actually have "neck" pickups mounted in the neck and bridge position and a "bridge" pickup in the physical middle position.
If you ever run into this problem, now you know.
I‘ve exchanged bridge and middle pickups and both the toggle array and the pickup selector today and the bass now works as I am spoiled to know any Dingwall should: Perfectly.
Thanks heaps to @AB Nate and this thread as well, I very much appreciate all of you contributing to the knowledge of the group!