NT Fretless 5: buzzing A string - setup question

[OldogNewTrick]

hi all

I have changed strings on my HB Daily5 from D'Addario ENR71-5 (half rounds 45-130) to EXL220-5 (40-125) requiring a full new setup.
I have tried everything from low neck relief & high action to strong back relief & low action and any combination in between.

I am stumped. My setups work nicely for all strings except for the A string, with the to be expected tonal changes in mwah and attack.
The A-string has a tendency to buzz, unless fretted (sic) extremely carefully mainly between the 5th and the 8th fret.

At a neck relief of 0,3mm the A buzzes from 3rd to 10th fret, (yet none of the others exhibit any buzzing). At a relief of 0,6mm the buzzing concentrates around the 5th to 9th fret. More relief doesn't change anything. The action is set at 2,0mm (G) to 2,4mm (B) with the other strings following the fretboard curve.

I have perused every available setup guide, don't know what to try next...

BTW, I found an old EXL220 A from another bass, did the same thing... haven't got a 3rd to try if both strings are maybe dodgy...

Any ideas?

[Benjamin Strange]

It could be a number of things - you could have some fretboard wear under that string, the nut may be cut too low, you may have a bad string. My guess is that you have some fretboard wear that needs to be sanded out.

[OldogNewTrick]

Originally Posted by Benjamin Strange

It could be a number of things - you could have some fretboard wear under that string, the nut may be cut too low, you may have a bad string. My guess is that you have some fretboard wear that needs to be sanded out.

Thanks, Benjamin.
Fretboard is clean and level.
I've shimmed the nut slot in order to eliminate that, but the nut slot affects only the open string, which doesn't / didn't buzz.

I guess I better order some fresh strings.....