The peek() seems to be working already, maybe only once in a while.
However, if vVersionDate contains 2/7/2015 12:00:00 AM, then simply using the variable value as a parameter to the date() function will produce an illegal script expression, like date(2/7/2015 12:00:00 AM) as VERSION_DT. QlikView cannot correctly interprete the parameter.
Again, use quotes to turn the value into a string which QlikView will be able to handle. Like