Error 10033 with eyelink package

Hi, I have a problem with eyelink, indeed while trying to run my script it stops when it arrives to TrialBegin command from the eyelink packages then I have the message : error 10033 the key is already associated with an element of this collection line : 16763. I dont understand since it there is nothing else under the same name and in my full script i dont have a line 16763 so where does the error come from ? Best, Clara