LM22676: LM22676 voltage drop

Part Number: LM22676

Hi,

I have a design that implemented on a board.

I use the LM22676 to convert 28V to 12V.

The board works but at the last year I have problem in some boards.

when I put a load of 1A the voltage drop down to 8.5V.

My question is what can cause that

Thanks

Shmuel