This is a problem due to how the iOS WebView works. Once the scanner is started the keyboard is automatically closed and can't inject any data once the scanner closes. This is something the Keyboard Wedge can't influence due to restrictions by Apple.
As this issue can't be fixed by us, we recommend using the Enterprise Browser (and adding a focus to the field in question), our Native SDK (if it is a hybrid app that you can modify), or the Barcode Scanner SDK for the Web (if it is a web app that you can modify).
Android and Windows are not affected by this problem.