There's probably a similair issue with triggerAttachObject (#15750).
But there's no alternative syntax (object as 2nd argument) available.

Hello,
is the problem still valid for you? We recently made changes in objects' IDs.

still valid, tested with DEV 1.23.125330

Could you please provide a repro mission?

added a repro mission: waypointAttachObject_bug.Stratis.zip
wp is a waypoint.
use addactions to execute the 2 different syntaxes

1. wp waypointAttachObject 66220
2. wp waypointAttachObject ((waypointPosition wp) nearestObject 66220)

check the hint for the result of "waypointAttachedObject wp"

Maybe triggerAttachObject can be looked at as well while at it? same problem

EDIT: ah, just noticed Master85 mentioned it already :)

i can confirm the problem. and.....
after a closer look :)

for "_i" from 1 to 5 do {
_wpBInfo = _wpArray select (floor(random 4)); [[13425,2,debb6400# 202594: house_k_1_ep1.p3d],[ID,buildingposIndex,Object],...
_hausID = _wpBInfo select 0;
_wpBPos = _wpBInfo select 1;
_haus = _wpBInfo select 2;
_wp =_grp addWaypoint [(_haus buildingPos _wpBPos),_i];
_wp setWPPos (_haus buildingPos _wpBPos); this is the essence!!!
_wp waypointAttachObject _hausID; try both
_wp waypointAttachObject ((_haus buildingPos _wpBPos) nearestObject (typeOf _haus)); last works first time for me.
_wp setWaypointHousePosition _wpBPos;
//_wp setWaypointCompletionRadius 3;
_wp setWaypointSpeed "LIMITED";
if (_i == TAC_Waypoints_group) then {

		_wp setwaypointtype "CYCLE";
				} else {
		_wp setWaypointType "MOVE";
					     };
			};

So the waypoints are (ZeusView) in center of the house, but the unit moves to the defined building position.

I am Happy now... ;)