I had trouble scanning the xpub key from the export with what is basically the insight.bitpay.com
qr-code scanner. It didn't work well but when it finally did, it skipped one letter of the xpub key. Later it even produced massive typos when scanning a normal address (which normally scanned well). Now I wonder which error correction level is applied when creating these codes. Did you do some analysis on how QR-Codes that get scanned wrongly might be interpreted as a different valid address?