BLF lights stay on; Transfers in limbo; Can't take incoming calls

Hello.

We have been experiencing some strange behavior and are trying to track the problem. On occasion, BLF lights for one or two extensions will remain on after hanging up. I’m thinking this is some sort of misinterpretation by Asterisk, and possibly as a result, incoming calls do not come through. Another odd issue is that call transfers to another extension get “stuck” and cannot be picked up by the destined extension or even recovered by the person making the transfer. Anyone have any ideas as to the cause of these problems? We are using the PIAF version 1.2 with FreePBX version 2.5.1.5.