Problem with slur priority

[Francisco Vila]

Hello,

\version "2.18.0"
\relative c' {
    \override TupletBracket.direction = #DOWN
    \tuplet 3/2 { f8[( e]) f }
    \tuplet 3/2 { g8[( f]) g }
    \tuplet 3/2 { a8[( g]) a }
    \tuplet 3/2 { b8[( a]) b }
}

What makes the slur jump under the tuplet bracket in the last tuplet? See image.
I can not set outside staff priority for the slur because that makes
the slur go completely outside staff.

It's worth noting that lilypond 2.0 (!) behaved correctly here, see
ms.29 of http://www.mutopiaproject.org/ftp/FaureG/O7/apres/apres-a4.pdf
, upper staff.

Thanks

-- 
Francisco Vila. Badajoz (Spain)
www.paconet.org , www.csmbadajoz.com