Create new mission, place just a group, player as leader. Write a short single line init.sqf like: call compile preprocessFileLineNumbers "basic.sqf";
create a "basic.sqf" flie with something like : hint "hello";
This is a way to have a report file without heavy script. Other methods certainly exist.
Run the preview, select a unit with F2... keys. escape, exit preview, read rpt in arma directory.
Unknown attribute itemsCmd
Unknown attribute itemsCmd
are added in the rpt file for this single unit selection.

Rpt log file is filled with some other reports, probably without relation with this specific warning. For instance, my very basic mission (one group, no enemy), during 10 sec play (preview) for selecting a unit, generates this rpt:

LODShape::AddLoadHandler: Handler not present in shape [a3\weapons_f\empty.p3d]
LODShape::AddLoadHandler: Handler not present in shape [a3\weapons_f\empty.p3d]
LODShape::AddLoadHandler: Handler not present in shape [a3\weapons_f_beta\acc\acco_hamr_f.p3d]
Attempt to override final function - bis_functions_list
Attempt to override final function - bis_functions_listpreinit
Attempt to override final function - bis_functions_listpostinit
Attempt to override final function - bis_functions_listrecompile
Attempt to override final function - bis_fnc_missiontaskslocal
Attempt to override final function - bis_fnc_missionconversationslocal
Attempt to override final function - bis_fnc_missionflow
soldier[B_soldier_LAT_F]:Some of magazines weren't stored in soldier Vest or Uniform?
soldier[B_soldier_LAT_F]:Some of magazines weren't stored in soldier Vest or Uniform?
Unknown attribute itemsCmd
Unknown attribute itemsCmd