Odd problem with E string only on new set of strings

[pafriend]

I have a Warwick Thumb 5 BO, fretless with lines. It came with a set of steel strings which I have finally squeezed the life out of. I decided to try a set of LaBella Slappers on a recommendation. They sound fantastic, except something very odd is going on with just the E string. There were some taper differences with the Warwick and LaBella strings, so I made some minor nut and bridge height adjustments, checked for truss rod relief, etc. On just the E I am having the following problems:

1. The characteristic growl present in all of the other strings in almost completely absent.
2. There is is an odd overtone to the sound, almost like something metallic is vibrating in the neck.
3. When I slide on just this string, at each fret line there is a distinct buzz over each line, which makes it sound like a slide on a fretted bass.

The sand job felt smooth when I first got the bass, though I am feeling a slight bump now over the fret lines, and I am guessing this is due to the difference in woods, and their response to changes in moisture. I have fiddled with truss rod adjustments, nut and bridge height, but nothing helps. What is even more strange is that the fretted sound of the slide does not occur on any of the other strings.

I've tried to come up with some possible causes. I am a newbie, so I tend to play a lot of exercises within a small range of the neck. Since I use roundwounds, I would expect more wear in this area, but I don't see much, and I've had the bass for less than six months. I wish I had enough time to play for wear to be an issue.

I ordered the strings via juststrings.com

Thanks in advance for any ideas.