I’m using custom-contexts to force long distance calls through a route that requires a PIN. We do this on our conference room phones to prevent random people from making long distance calls. The conference room phones are using ZAP extensions (they are analog phones and we are using an astribank). The pin works great for 1 outbound call, but if the user tries to place a second simultaneous call, they are prompted for the PIN - but the PIN is rejected. It fails with “Password incorrect”.
Did you try turning on DTMF debugging? What does the Asterisk CLI report then for digits being received? Are the digits being duplicated, perhaps? If so, you can turn off hardware based DTMF_Detection to help resolve this.
Let me know if this is still an issue for you and i will post how to disable this.