Bug in Cluster spanner?

[V!ctor Adán]

Hello Lilyponders,

I'm using ramp-style Cluster spanners and I'm getting unexpected output.
When more than two identical chords follow each other, the upper boundary of the cluster collapses down one space and then goes back up. 
In the example below (its corresponding image is attached), I have a sequence of 5 different chords, each repeated 4 times. Notice how the Cluster collapses in the two middle chords of each set. This is not what one would expect since all 4 chords are identical.   
Notice also how the collapsing of the cluster's vertical span does not happen when we use stairs-styled clusters. 
So, is this a bug? I'd really like this not to happen...

One more thing. Notice that I've added a rest (r4) between the ramp-styled cluster and the stairs-style cluster. If we remove the rest, the style change does not take effect. It is as if the Lilypond compiler was ignoring the second \makeCluster marker and was fusing the two cluster because of their temporal contiguity...

Thoughts, suggestions?

Many thanks,

Victor

%%%%% START %%%%%
\version "2.11.45"
mycluster = \makeClusters{
   <g' g'>4 <g' g'> <g' g'> <g' g'>
   <f' a'> <f' a'> <f' a'> <f' a'>
   <e' b'> <e' b'> <e' b'> <e' b'>
   <d' c''> <d' c''> <d' c''> <d' c''>
   <c' d''> <c' d''> <c' d''> }
{
      \override ClusterSpanner #'style = #'ramp
      \mycluster
      r4
      \override ClusterSpanner #'style = #'leftsided-stairs
      \mycluster
}

%%%%% END %%%%%

cluster_problem.png
Description: PNG image