There might be various cases of how that problem becomes visible.
1) If your original video or webinar is in sync with audio
Please check whether desync appears during the recording itself, or only after saving it into a video file. In order to check that, please record a short test video, stop recording and check video and audio sync in Screen Capture's preview window.
If the sync issue does not appear in the preview, try selecting any other output format or change video and audio codecs in selected format settings.
To access format settings, click on Save as and white cogwheel button and select different codecs at the Video tab and Audio tab.
Then click OK and save the recorded file again, and check video and audio sync in the resulting video file.
If desync does appear in the preview, it means that video and audio were recorded with no sync.
Delete this recording and then go to Settings - Preferences - Video menu. Set Frame rate to 25 FPS, turn off Intel and/or NVIDIA hardware accelerations (if enabled), and also turn off option Disable Aero theme during capture (Windows Vista / 7). Then click OK and try recording your video again.
If de-sync still occurs after changing output format/adjusting program preferences, please contact us so that we could investigate the issue further.
2) Your original video or a webinar starts to desync when the recording is started.
Screen recording requires certain resources, so if many applications are launched at the same time, it might not be enough to record the screen properly.
If you record a video from the browser, try changing the browser and close all the unnecessary tabs.
It is also possible to decrease the frame rate.
If you are a PC user, updating your drivers might also improve the performance and quality of the output video.
One more solution is using the alternative capture mode that can be found in the menu Settings - Preferences - Video.
If you are a Mac user, in addition to changing your browser and closing all the unnecessary apps, you can try changing the frame rate to 25 FPS.