Attended Transfers end up going to the ether

I have calls coming in from analog lines from a Digium AEX2400, when someone does an attended transfer from our Grandstream GXP2160 phones to another extension, sometimes when someone picks up the phone it doesn’t pickup the call and goes to the ether, usually the case is if they pick up the phone within the first ring this happens but it doesn’t happen all the time so it’s inconsistent. Does anyone know what’s causing this behavior?

Edit: I tried changing DTMF Signaling to SIP INFO and didn’t fix the problem, I also changed from PJSIP driver to CHAN_SIP and things got worse, when someone would transfer a call I would have to wait like 15 seconds before I could actually talk to someone and also during a conversation the phone would basically stop all audio on a call and BLF lights would get stuck on.