Different QR Code scanning distance with iPad Mini 4?

Question

we have written a QR code scanning App that (roughly) creates a AVCaptureSession, adding the front camera as a AVCaptureFigVideoDevice to the session, calls startRunning on the session, and then handling the didOutputMetadataObjects callback, looking for QRCode data.

This has always worked GREAT but then our client noticed a drastic distance using the iPad mini 4 (we were previously running on iPad mini 2s), he must hold the item to be scanned much farther away from the camera, when you hold it closer it doesn't scan, and in the preview it looks relatively blurry.

Both iPads have iOS11 on them, the only difference we can see is the hardware, iPad mini 2 vs 4.

Is there some setting that needs to be configured on the mini4 differently than mini2 for the camera? It looks to be a focusing issue, maybe the lens has changed. What settings should we look at in order to get it to focus on a relatively close object, like it was able to do on the previous hardware?

Thanks very much for any thoughts.