Due SPIFLASH - only one time writing on SPIFlash chip


I have a Due with 5" CTE 800x480 display with an flash chip on. Im using spiflash lib.
I can read bytes from a single page of storage chip - no problem. I can write bytes to a single page. But this i can do only one time then it will not write any more without any message.

Any idea what is wrong?

the code for reading:

void DecodingPage()
byte line1;
byte line2;
myFlash.readPage(0x001); // Page 1
line1 = myFlash.buffer[0];
line2 = myFlash.buffer[1];

for writing

myFlash.buffer[0] = line1;
myFlash.buffer[1] = line2;
myFlash.writePage(0x001); // Page 1