# Analogic pin 0 (pin 14) problem UNO board

I have an Arduino Project developped for an UNO Arduino Board; the sketch have a size of 30000 bytes aprox.

The whole set of features requeried works perfectly, but I have a problem with the A0 pin

In input mode Early, on the project developement, I tried to use the A0 pin to read three buttons linked with resistors; after many issues, a change to the pin A1 solved the problem.

In output mode On a later phase of the project, when I have occupied the rest of pins, I need to sent digital signal by the A0 pin... really the signal is sent by a function that send to digital 2, A2 and A3 pins also; but as in the referred pins the signal it's constant, on the A0 pin seems flickering

I tried to change many questions of the software, but isn't effective. So, this occurs on three UNO original boards and three selfmade boards with the chip and the bootloader uploaded -the A0 pin incorrect on the board it's statistically discarded ;) -

Any idea to resolve this?

void setup () {