No experience with the Xperia, but you might want to see if it will focus on anything when in the mode you are using to scan the QR code. If it is a focus issue with the Xperia, not sure what to tell you.
Since it's an Android phone, one thing I could recommend is use of a program called Barcode Scanner. I use it for many things, and its autofocus firmware seems to drive my Galaxy S8 very well.
Find it here >> https://play.google.com/store/apps/details?id=com.google.zxing.client.android
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.