I have never encountered a "predictive number feature option", on a phone, (unlike predictive text, that compares input to a dictionary).I have seen some mobiles compare to an internal directory as you dial, but I have never dialled so fast that it has affected the phone, I'm not certain how that could be possible. The device can usually handle input faster than a person can move their fingers.
It is it just one user that is having issues? If it is, then it might be a considered incorect use of the phone, a "user" error, and they may have to change their dialling habits. I'm sure that Yealink did not intend the phone to fail when used as expected.
Have you tried eliminating the phones local directory?