weird vibrato

The Problem:

            When I play back my scores, I find that often the top instrument has an aggressive vibrato. Is there any way to solve this problem without reverting to factory settings as, I have a problem with my musecore files in which some files cannot open again because my computer cannot read them. I also have many scores open and do not want to loose them.

How I Came About The Problem:

             I was fiddling around with the synthesizer and, i must have pressed a wrong button or something as, when i returned to my score, now the top line had this aggressive vibrato however all other instruments were fine.

Extra Info:

            Any help is needed, and appreciated. I will not revert to factory settings