If you hear when two people are talking, the volume gets lowered; this suggests the effects of echo cancelation. Ducking is an effect of echo cancelation. Each participant's browser can auto-compensate for perceived echoes/feedback during the session if echo cancellation is used. Please look at our support doc, which has more info here: Echo Cancellation & Avoiding Volume Ducking. Disabling echo cancelation in future sessions can help improve quality. 

Alternatively, the session's cloud backups can be accessed and downloaded from the Dashboard, unaffected by echo cancellation. Next to the Recent Primary Recordings tab, you can select the Down Arrow and choose the Backup Recordings Option. From there, sessions will be displayed for selection. You can choose your session and select the session's down arrow to view and download any available backup recordings.