The walls dont have any Parents after the latest update.
configfile >> "CfgVehicles" >> "Land_Mil_WallBig_4m_F" have parents

["Wall_F","Wall","NonStrategic","Building","Static","All"]

But if you do:

hint format ["%1", nearestObjects[(position this nearestobject 1769489),["Wall_F","Wall"],200]];

Then it will return [] for you and before the update it worked fine.

It could be something with the last SPOTREP #00011:
"Potential Altis performance optimization (especially when using a lot of AI units): removed class properties from models in Structures_F that don't need it"