Can you gather a PRT illustrating this issue? Settings > Help > Send Problem Report
You may want to open a TAC case with the PRT and timerange when the echo is observed so we can take a look into the issue. I just tested a video call with Jabber for TelePresence cloud and did not observe any echo problems. Do you only observe the echo problem when on an audio-only call registered to a CUCM on-prem?