T4x DSSKey extension issue

[Kamiware]

Dears,

I auto-provision T4x phones.

I push something like this to the phones:

linekey.3.label = Name
linekey.3.line = 1
linekey.3.pickup_value = **
linekey.3.type = 16
linekey.3.value = 500


Now on 90% of the phones, this works as expected. (While phone is idle, on keypress call is made to 500, when phone is ringing, on keypress call is made to **500)

Nowever some phones, decide to make calls to ** (without anything more). More specific, The most often case is when there is someone on the line, and the person operating the phone want to transfer this person TO another extension, then they press the button, and the call to ** is made.

Is it possible to explain to me what setting this could be?

Thanks,
Samuel