Call Flow: H225 setup ISDN setup with 1 PI with 2 PIs ------originating gateway (OGW)----->terminating gateway (TGW)---->time-division multiplexing (TDM) Switch
Sending two Progress Indicators (PIs) should not cause any call failure. A PI is optional information and can cause problems with busy-tone, ring-back tone, or an announcement but not an actual call failure.
It is fine to have two PIs in one message according to the Q.931 standard, section 4.5.23:
"The purpose of the Progress Indicator information element is to describe an event which has occurred during the life of a call. The information element may occur two times in a message."