Is iOS 9.2.1 now causing original fingerprint sensor to fail?

I'm a repair tech at a phone repair shop. After the iOS 9.2.1 update I've had a couple of customers' iPhone 6's fingerprint sensor fail to work after replacing their LCD assembly. Their original home buttons were in good shape and transferred to the new screen. The only change was the new LCD assembly. We do 100's of these repairs a month and I am confident that the connections and repair were all good. In both cases, the customers' phones were already updated to iOS 9.2.1 before the repair. I had the customers delete their existing fingerprints and re-enter, but the sensor would not even read a print for set up. I have not yet tried a factory reset or DFU recovery in these cases because the customers were in a hurry. Has any one experienced the same situation or found a solution?