Motor in borewell got stuck

The motor in my borewell got stuck and mechanic tried to pull it up using pulley but it didn’t worked. They used pressure pump also and declared it might be caused by landslide internally and it cannot be retrieved. It is a new bore and also mechanic mentioned that 4mm pipe might have been used and suggested to go for a new borewell which will cost more. Please help if there are any better option to get the existing one corrected.