Piston-to-valve interference does not occur at TDC.
It occurs when the piston is descending on the intake stroke, and the opening inlet valve catches up with the descending piston.
It occurs on the exhaust stroke when the rising piston catches up with the closing exhaust valve.
Intake interference occurs when the cam is either much too advanced, or there is insufficient notch depth in the piston for the valve motion.
Exhaust interference occurs when the cam is much too retarded, or there is too little notch depth.