Design failure? The Fender 5-strings that appeared in the late 90's/early 2000's were a failure, IMHO. Very floppy B strings and lots of weird dead spots.
In the words of bass guru Ed Cannacci (Gelb Music, Redwood City, CA), "The B strings on Fender 5-strings from the late 90's to 2001 or so, just didn't work."
In-line 5-string head stock is the giveaway:
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My son had an American Jazz 5 string cir 2001. No dead spots or floppy B Strings. Used GHS bass boomers on it, I believe a .125 gauge B. What I did notice was a very slight tonal characteristic change going from the E to the B string when played in the ensemble, one would never notice it.
As for the OP, I’ll use an analogy. Back in the 60s Volkswagen beetles were extremely popular, but only a few were much interested in the Fastback or Squareback. They were great cars, much better and more practical than the venerable beetle, but They didn’t sell any where near as many as it wasn’t what Volkswagon was known for.
To this day, when I think of a Fender bass, I think of the 4 string JB, PB, and the PJ. The 5er just seams odd.