Error in FIND function

I am trying to use the Find Function but keep getting an error message every time I try to save the calculated column. I am trying to find the "(" text within a text column and PBI throws an error stating that "The Search Text provided to function "FIND" could not be found in the given text." Here's an example of the column for the "given text":

Aircraft (Serial #)      Aircraft Type

AS365 (65533)

AW139 (399443)

S-92 (7649246)

I am trying to pull out the "Aircraft" type from the "Aircraft (Serial #)" column so my formula is:

Aircraft Type =

                     LEFT( [Aircraft (Serial #)],

                               FIND( "(", [Aircraft (Serial #)] ) - 1

                            )

It seems that the FIND function in DAX will not accept the "(" as the text to find, and instead assumes that the "(" is part of the formula. It of course works fine in Excel.