\partcombine error with hairpins

[Miguel Jesus]

I'm having a problem with \partcombine (I'm sorry for the long examples but 
this is the code I'm working with right now). With this code the voices 
aren't combined properly:

\language "portugues"
\version "2.18.0"

\layout { \context { \Score skipBars = ##t }}

bassoonOneFileOne =  \relative re' {
  \clef "bass" \key re\major \time 12/8 \tempo 4. = 90 
  si1.\> | sib1.\< | si1.\> | sib1.\< | si1.\> |
  sib1.\< | si1.\> | sib1.\< | si1.*1/2\> s2.\< |
  \time 4/4 \tempo 4 = 130 R1*8\! |
  \key re\minor re,1\ff | mib1 | \tempo 4 = 80
  re1 | mib1 | re1 | mib1 | }

bassoonTwoFileOne =  \relative re' {
  \clef "bass" \key re\major \time 12/8 \tempo 4.=90 
  si1.\> | sib1.\< | si1.\> | sib1.\< | si1.\> |
  sib1.\< | si1.\> | sib1.\< | si1.*1/2\> s2.\< |
  \time 4/4 \tempo 4 = 130 R1*4\! | la,2 sols2 |
  fa2 mi2 | re1 ~ | re1 |
  \key re\minor re'1\ff | mib1 | \tempo 4 = 80
  re1 | mib1 | re1 | mib1 | }

\score {
   \new Staff { \partcombine \bassoonOneFileOne \bassoonTwoFileOne }}


At first I thought it had to do with the spacer rests but even without them 
the problem remains. The output is right if I remove the crescendos and 
diminuendos.

\language "portugues"
\version "2.18.0"

\layout { \context { \Score skipBars = ##t }}

bassoonOneFileOne =  \relative re' {
  \clef "bass" \key re\major \time 12/8 \tempo 4. = 90 
  si1.\> | sib1.\< | si1.\! | sib1. | si1. |
  sib1. | si1. | sib1. | si1.*1/2 s2. |
  \time 4/4 \tempo 4 = 130 R1*8 |
  \key re\minor re,1\ff | mib1 | \tempo 4 = 80
  re1 | mib1 | re1 | mib1 | }

bassoonTwoFileOne =  \relative re' {
  \clef "bass" \key re\major \time 12/8 \tempo 4.=90 
  si1.\> | sib1.\< | si1.\! | sib1. | si1. |
  sib1. | si1. | sib1. | si1.*1/2 s2. |
  \time 4/4 \tempo 4 = 130 R1*4 | la,2 sols2 |
  fa2 mi2 | re1 ~ | re1 |
  \key re\minor re'1\ff | mib1 | \tempo 4 = 80
  re1 | mib1 | re1 | mib1 | }

\score {
   \new Staff { \partcombine \bassoonOneFileOne \bassoonTwoFileOne }}


If I add one more crescendo or diminuendo after that the whole thing goes 
wrong again.

Once again, sorry for the long code. Thanks, Miguel