My operator doesn't close the window all the way

My present operator does not close casement window all the way. I turn the operator handle till it can't turn any more due to arm hitting the sill. At this point I can pull the window closed and lock it since it is only a cm. from being closed. Is this an operator issue that can be solved by replacing or repairing operator. I believe your 39=317 operator is the replacement.

Thank you