Travler 8.5.1 facing lookup issue on corporate "Group"

Hi,My Lotus Notes Traveler 8.5.1.2 Build 201003232022 running on Lotus Domino server Release 8.5.1FP1 (64bit).

Our iPhone users complaint that they are not able to perform groups lookup from our Corporate Address Book.

Lookup works fine for all corporate address book ONLY on individuals.

Help require urgently please!

Configuration issue or traveler known issue?

Regards,

Lee LK