Lilypond: Different vertical space

Question

Sometimes (not every time) when a song (because of the lyrics under the score) takes two pages Lilypond adds an extra space between the lines. How to avoid it?

First image regular space:

Second image extra space:

code for lyrics under the score: (usually one with the original language and one with translation)

\markup\fill-line
{
   \left-column
   {
   \vspace #2

   \line {original language}
   \line {original language}
   }
}

\markup\fill-line
{
  \left-column
  {
  \vspace #2

  \line {translation}
  \line {translation}
 } }