If the value string for a QR Code is greater than 100 characters the resulting QR Code cannot be scanned. Here's a StackBlitz demonstrating the issue:

https://stackblitz.com/edit/angular-2axafs?file=app/app.component.ts

Interestingly enough, this issue doesn't seem to be present in the AJAX version of the QR Code component as putting in a +100 character string on the example page results in a valid QR Code: https://demos.telerik.com/aspnet-ajax/barcode/examples/qrcode/defaultcs.aspx