I put a set of D'Addario Slowounds on my Jazz to mellow it out and my E string won't intonate. I get it intonated before using DR Moonbeams, so I know it's not the bridge. Now my flippin' E string is seriously flat at the 12th fret regardless of how far forward I move the bridge saddle. The B string on my Thumb BO 5 did the same thing. Broken cores on both? Has anyone else had this problem with Slowounds? D'Addario XLs are my usual string. Anyone have any suggestions for sturdy strings before I pick up another set of XLs?