Always crashes when touching keypad during calls

Question

Zoiper 1.43 for Android crashes everytime when I make calls and touch a num key on the zioper keypad.

How can I resolve it?

Thanks.

Android 5.1

accounts > features > DTMF style:  inbound

Zoiper versions:

    1.43 crashes 100% on the first DTMF key touch

    1.40, 1.39 and 1.38 no problem