Hi Its Windy,
We land on VIDP 29 everyday, it is present in our database and I never turn the terrain off. Please check your EGPWS database, our current database is version 451 and that contains both 29 and 11 in it.
May be your company can issue an internal alert asking pilots to switch off terrain mode when making an approach on runway 29 or 11.

DesiPilot