PLSQL query runs in four seconds but Lobby Element times out

I have a created a Lobby element which is timing out.  I am logged on as user IFSAPP.  The result is the same for two other users.  The PL/SQL query behind the element returns the FIVE records in FOUR seconds

select

contract,

part_no,

ifsapp.inventory_part_cfp.Get_Cf$_Qty_Demand (contract,part_no) qty_demand

from inventory_part ip

where ip.PART_STATUS = 'C'

and ip.CONTRACT = 'PCT'

and ifsapp.inventory_part_cfp.Get_Cf$_Qty_Demand (contract,part_no) >0

The Lobby Data source I have created with the same query takes 90 seconds to populate with either “&AO” or “ifsapp” prefix

The Lobby element times out and doesn’t return any data after 2 minutes.

The Custom Field referred to is using a select statement:

select ipa.qty_demand from ifsapp.INV_PART_CONFIG_PROJECT_ALT ipa
where ipa.contract = :contract and ipa.part_no = :part_no

Does anyone have any suggestions why the disparity or how to resolve?

Many thanks!