Gmail body information extract issue

Question

I have almost no experience in coding but I've developed a simple code to extract information from tagged emails.

function getemails() {
    var label = GmailApp.getUserLabelByName("Test");
    var threads = label.getThreads(); // ARRAY

    for (i=0;i<threads.length;i++)
  {

      SpreadsheetApp.getActiveSpreadsheet().getRange("B"+(i+1)).setValue(threads[i].getMessages()[0].getPlainBody())
  }
}

It works with all my tags but It has I've encountered a problem with some of the emails and I was hoping maybe someone could help me fix it.

The emails I'm trying to read have this in the begging of their body:

------------------------------------------------------------------------------------------------------ 

And for some reason, when extracting the body information, what I get in the value is:

--
id: 7898659753248090

If I remove that line, the body information is extracted perfectly, so the problem is that line.

Is there any way to fix this?