I just replaced a tip this last week with a customer with the same problem.Ok on centre hit, but only sometimes on draw was it making a tink sound. I tried it out and found the area, initially I thought it was not glued properly. The tip was a LePro. I don't have those, so cut off the tip, customer chose another tip. The tink went away.
The glue around the old tip looked fine, but the area that was making the noise, looked to be coming apart or delaminating, even though it is not a laminated tip.
I have also seen where ferrules have not been faced correctly, and the outer edge of the ferrule is lower than the centre.When glued, there was not enough to properly adhere the tip entirely, ie they could not of had glue all round the circumference of the tip. They would also make a tink when struck on the outer edge of the tip.