As you have found, there can be sync problems when the audio and video are recorded on different devices.
Try this workaround: Control-click on the audio clip. In the drop down menu that appears, choose Show Speed Editor. That will reveal an audio speed adjustment handle in the upper right hand corner of the audio clip. Now use the slider above the timeline to the right to expand out your timeline. Then use the speed adjustment handle to slightly vary the speed of the clip to bring it into sync with the video. Sliding the handle to the left increases the speed. Sliding to the right decreases the speed. You might need to split the audio clip in appropriate places and sync the separate segments.
You can use the above procedure on the video clip as well, to align it with the audio.
You may also find it helpful to slide the detached audio clip slightly to bring it into sync. You can drag it with your cursor. Or, a more precise way, is to select the audio clip and, while holding down the Option key, tap the < key to nudge the clip one frame to the left with each tap. The procedure doesn't work for nudging right, so you would need to position the clip slightly to the right and then nudge it left until synced. Again, you might need to split the audio clip at appropriate points and work with the segments.
-- Rich