When you get a memory issue after installing a new iOS update, it might just be a tiny problem in the iPhone software owing to recent changes. Normally, difficulties like this may be readily resolved by restarting the iPhone, so if you haven't already, try that and see if it solves the problem. Here's how to do it:

• To begin, hold down the Power button for a few seconds or until the Slide to Power Off slider displays. To totally turn off your iPhone, drag the slider. To reset, wait around 30 seconds and then hit the Power button again.
• You may turn off your iPhone in the settings menu if you're running iOS 11 or later. Simply navigate to Settings-> General-> Shut Down from the main menu. Allow your iPhone to rest for at least 30 seconds to 1 minute before using it again. an then press the power button