Another bit of information, I don’t know if it’s pertinent or not: I have set the ring groups to ignore busy extensions, because if the phone rings while someone is on a call, they then cannot park that call. This still happens, although much less frequently, if someone makes an extension to extension call within the office to someone who is on a call. Again, the end result is that if the phone rings while a call is in progress, then parking does not work on that call.