Why doesn’t the “a” work when I replace the digitizer?

I have replaced many digitizers for many iPads. From second generations on to airs to minis, that being said I can say that it is not my first rodeo. My problem is with the iPad Air 1. When I replace the digitizer the “a” works only on the landscape keyboard if you press with your thumb on the screen and finger behind the device. It is only the “a” in landscape mode not portrait, I have tested for dead spots by moving icons and there is none. I have tried other digitizers from different companies with the same results. The “a” worked before digitizer replacement. I am at a loss to get a remedy for the problem, any help would be greatly appreciated. Thanks.