Why is only one side of a call being recorded instead of both parties?

There are two possible reasons for one-sided call recording: (1) Another call recording app is installed on the target device, which conflicts with TheOneSpy recording. Uninstalling the third-party call recorder may resolve the issue. (2) A recent Android system update may have disabled this feature at the OS level. In the second case, the feature cannot be restored by TheOneSpy because it is disabled from the system end.