Thanks for the additional details.
Are these two digipi's? client being driven by RadioMail on IOS? The client
digipi is in TNC mode or AX.25 mode? (I don't have radiomail here).
It might be helpful to see the PktLog on the client digipi.
This looks a bit like the ax.25 protocol failure we've seen recently.
I've also seen it hang on the same email over and over,
deleting/receiving the email clears it.
In the end, both client and server are indicating "RR" Ready-to-Receive,
so they're
waiting on each other. The client eventually DISConnects and the server
obliges (UA)
curiously,
-craig
KM6LYW