Maybe there was a "Low Memory" warning on your device.

You may reboot your device and then turn off some apps in the background to save memory:
1. double-tap the Home button to bring up the list of running apps
2. simply swipe upwards on the thumbnail to dismiss it

3. restart CamScanner to try again.

If it doesn't work, please report bug to us as follows:

go to settings of CamScanner->Suggestion & Feedback->describe your problem in detail (how can we reproduce your issue) and confirm your email address->tap "send" at upper right corner

Once we got your log, we will investigate your problem and get back to you as soon as possible.