The handset lifter is equipped with both a ring tone level detechtion and a frequency detector. Some phones might have a level and a frequency that the HSL have difficulty in learning. This can give you some unwanted behaviour from the HSL together with some phones.

Please try to do the following:

1. If possible try adjust the ring tone level on the phone prior the learning process.
2. If possible try to change the pitch of the ring tone prior the learning process.