What if measurement is wrong in sale deed or registry?

I have recently purchased plot of 25*40 and started construction of my home. Base pillar work has been completed and then neighbor started questioning and asking us to stop construction. It seems they are supposed to have 40ft area but left with 25ft.In the society map our property size is 20*40 and for our neighbors 20*25 but in their registry document they have 20*40. It seems the measurement of plots was not done correctly and their registry document and plot size has some dispute. Now they are asking 6ft property form us. We are asking all our neighbors to give 2ft each but no one is agreeing and society guy also not accepting the mistake as the guy who did measurements and registration is no more. We paid for 20*40 plot size why should I be the one to give my 6ft property.