I am experiencing problems with sonus dtmf. I tried setting different parameters related to the RTP BUGS listed in switch_types.h but it did not seem to fix the problem.

I have freeswitch ----> [carrier(sonus), ...]  -----> freeswitch

freeswitch sends the following digits to our carrier, and is received by the other end (also a freeswitch) missing the digits marked in black.
pcap shows the missing digits as being part of the previous packet, so two 1's becomes one 1 with the duration sum of two.
 
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What are the relevant parameters I should set?