basic warranty terms for such project gadgets is 12 months from date of purchase, after lapse of 6 months the replacement is always charged at pro-rate adjustment. Plus the user has to pay for shipping & handling. The online shops does not handle warranty issues they always ask user to approach manufacturer with proof of purchase.
with the equipment serial no & proof of purchase you shall contact Raspberry foundation. in 2018 we worked with team of engineers for a pilot project for solar power array based traffic signals system in a selected locality of Karachi.
The engineers used Raspberry Pi 3 variant something, as control engines, some engines failed in 7 months and thats how we came to know warranty claim procedure. The advantage we have is logistics to manage warranty we paid only 15% of new equipment price under warranty claim.