Fretless help

[Fretless_Wanted]

I got a new bass, and made my old Squire P-Bass into a fretless. Well, the guy at the music store did it for me, I was too scared (And my parents didn’t want me to) pull the frets out myself, but he ended up filling them, too. Anyway, I got it back yesterday, and it was pretty good. But today, i think the filler the guy used shrank a lot. Also, higher up on the neck, and especially on the D and G strings, I get a really bad vibration of the strings off the wood, making a high pitched buzz. I also know he didn’t sand it or anything. I’ve adjusted the truss rod, trying to make the neck straighter, but I can’t git rid of the sound.
I love playing on it, but the vibration of the strings makes it hard to play, what with the sound being very annoying.
Do you know what could cause this? I’m planning on taking it back to the music store tomorrow, but any idea could help.

And would sanding down and refilling the frets where the filler shrank help this?

[Jongsch]

I did the same thing to my squier, and it came out pretty good. It was a couple of years ago, so my memory is a bit fuzzy, but I think I used plastic wood to fill the fret gaps. To smooth it out, I sanded the board, then put a couple of coats of polyurethane on it (I think I also might have sanded with a fine grain after each coat except the last one). A bit of the finish dripped down to the back of the neck, so its a bit bumpy where the thumb slides, but it doesn't bother me, and I'm overall pleased with the results.