Cannot retrieve on hold calls

[subric]

We've been having this issue where the customer cannot retrieve calls on hold. It is happening randomly.
They are using CTI with genesys for call routing. So it's on a soft phone.
Today, I captured several calls which have failed to retrieve the held caller.

Every time it fails, I noticed the CODEC change to T.38 from G.729A.
How is this possible? I thought T.38 was for fax. Could it be a bug?

I have verified with the users that the call cannot be retrieve when the call logs codec t.38

KEY 4 SCR MARP TERMHOLD TN 008 0 13 14

ORIG VTN 252 0 01 16 VTRK IPTI RMBR 127 49 INCOMING VOIP GW CALL
FAR-END H.323 SIGNALLING IP: 159.208.160.234
FAR-END MEDIA ENDPOINT IP: 159.208.160.240 PORT: 5256
FAR-END VendorID: Nortel_CSE_1000;ssLinux-6.00.18
TERM TN 008 0 13 14 KEY 4 SCR MARP CUST 0 DN 8969 TYPE 3905
VGW TN 008 0 15 22 TS 50
SIGNALLING ENCRYPTION: INSEC
MEDIA ENDPOINT IP: 10.60.252.136 PORT: 5244
MEDIA PROFILE: CODEC G.729A NO-LAW PAYLOAD 30 ms VAD OFF

----------------------------------------------------------

KEY 4 SCR MARP ACTIVE TN 008 0 13 14

ORIG VTN 252 0 01 16 VTRK IPTI RMBR 127 49 INCOMING VOIP GW CALL
FAR-END H.323 SIGNALLING IP: 159.208.160.234
FAR-END MEDIA ENDPOINT IP: 159.208.160.240 PORT: 5256
FAR-END VendorID: Nortel_CSE_1000;ssLinux-6.00.18
TERM TN 008 0 13 14 KEY 4 SCR MARP CUST 0 DN 8969 TYPE 3905
VGW TN 008 0 15 22 TS 50
SIGNALLING ENCRYPTION: INSEC
MEDIA ENDPOINT IP: 10.60.252.136 PORT: 5244
MEDIA PROFILE: CODEC T.38 NO-LAW PAYLOAD 1 ms VAD OFF

any ideas?