Hi
I cant find the Markley ones on the web in the UK, however the Thomastik Jazz flat wound .043.056.070.100.136 may do the trick
I'm kind of feeling my way around the fretless stuff, but I want the warmest that does the elast damange to the fret board, it's a Macassar fretboard.
As Dave says it's probably just the nature of the bass
Andy