ARSession and AVCaptureSession

Hi,I would appreciate if you could help me . In my project, I use AVFoundation custom camera function to achieve the scanning function, the use of ARKit achieve ar function. Sweep pages and AR pages are independent ViewController, both through the viewController container management. But I encountered a problem, first open the ar page and then switch to the scan page, the scanning function is normal use, but the AR page will appear to identify the image of the problem. If you first start scanning function, and then switch to the AR page will not be the problem, there is a quick switch between the two, then the AR page will not identify the image of the problem, I did not find the relevant online Information, hope to get your help