How to stop a endless loop

I uploaded a sketch long time ago and now trying to replace with other. The problem is that it is stuck in a endless loop that is not possible to break. I have tried to connect RST with GND but no reaction. On the serial monitor the lines with the old code just entering new lines. One error message is "SendtoWait failed"
It is a chineese copy and the reset button has left the board... but still, is it possible to clear the processor in some way?

Reburn the bootloader.

Not possible, the board does not respond at all, just looping some lines of code and the error message

Is there a way to do "a total reset" of a Nano?

Did you try to burn the bootloader using ICSP .

Eeeh.. used bootloader in Arduino under Tools... Please explain ICSP.

OK the ICSP is the 8 pin connector. I am using the USB on the board, Works fine with other Nanos.

This best explains it:

Tnx Larry! Will check this!

Just connect the RESET pin to the GND pin momentarily.

Tried that, no change.... the loop is just going on. It would be easy to just throw the Nano but at this time it has became more of a principle to solve it... I mean, how hard can it be..?

Have you installed a new bootloader yet?