One way audio over VPN

Question

I have 2 Cisco 1941 routers with a standard IPSec tunnel between them. Data works fine, but VoIP is encountering a one way audio issue where the remote site calling cannot be heard but they can hear me.  This seems to match what I'm seeing in encaps and decaps. The quesion I'm having is why would the remote site be encapsulating all packets but the office router isn't decaping these audio packets. I isolated one phone specifically so that's why the SA is for only 1 host.
Thanks!
OFFICE ROUTER
   protected vrf: (none)
   local  ident (addr/mask/prot/port): (192.168.0.0/255.255.0.0/0/0)
   remote ident (addr/mask/prot/port): (10.90.91.6/255.255.255.255/0/0)
   current_peer REMOTE_IP port 4500
     PERMIT, flags={origin_is_acl,}
    #pkts encaps: 4104, #pkts encrypt: 4104, #pkts digest: 4104
    #pkts decaps: 375, #pkts decrypt: 375, #pkts verify: 375
    #pkts compressed: 0, #pkts decompressed: 0
    #pkts not compressed: 0, #pkts compr. failed: 0
    #pkts not decompressed: 0, #pkts decompress failed: 0
    #send errors 1, #recv errors 0
     local crypto endpt.: 192.168.0.227, remote crypto endpt.: REMOTE_IP
     path mtu 1500, ip mtu 1500, ip mtu idb GigabitEthernet0/0
     current outbound spi: 0x69C77389(1774678921)
     PFS (Y/N): N, DH group: none
     inbound esp sas:
      spi: 0xEA4A3FF9(3930734585)
        transform: esp-3des esp-sha-hmac ,
        in use settings ={Tunnel UDP-Encaps, }
        conn id: 2095, flow_id: Onboard VPN:95, sibling_flags 80000046, crypto map: VPN_MAP
        sa timing: remaining key lifetime (k/sec): (4409444/1207)
        IV size: 8 bytes
        replay detection support: Y
        Status: ACTIVE
REMOTE ROUTER
   protected vrf: (none)
   local  ident (addr/mask/prot/port): (10.90.91.6/255.255.255.255/0/0)
   remote ident (addr/mask/prot/port): (192.168.0.0/255.255.0.0/0/0)
   current_peer IP_OFFICE port 4500
     PERMIT, flags={origin_is_acl,}
    #pkts encaps: 4055, #pkts encrypt: 4055, #pkts digest: 4055
    #pkts decaps: 4099, #pkts decrypt: 4099, #pkts verify: 4099
    #pkts compressed: 0, #pkts decompressed: 0
    #pkts not compressed: 0, #pkts compr. failed: 0
    #pkts not decompressed: 0, #pkts decompress failed: 0
    #send errors 0, #recv errors 0
     local crypto endpt.: IP_REMOTE, remote crypto endpt.: IP_OFFICE
     path mtu 1500, ip mtu 1500, ip mtu idb GigabitEthernet0/0
     current outbound spi: 0xEA4A3FF9(3930734585)
     PFS (Y/N): N, DH group: none

Answer 1

Thanks Michal.
1) I have taken these buffer captures. The capture associated with "outside" is short when compared with the number of packets from the "inside" capture in the amount that is most likely associated with the call we placed.
2) Not NAT at all.
3) No CBAC or ZBF, unless some default that I'm not aware of. Not sure off hand how to disable those.
I did get this case through to TAC but after 3 hours we are left at comparing the capture buffers.