Ur computer is a physical system and some aspects of it uncomputable. You cant approximate or predict everything. Picture it as billiard balls modeling a circuit, you can’t tell whether it halts, meaning you don’t know where the balls will be.

Or a program that knocks out a bottle when it finds a counter example for whatever . U can’t tell whether it will spill the liquid.

And you have as well the problems of approximating the continuous with bits, you’ll always lose information