Custom workflow getting into error

Hi,

We are using custom workflow for approval hierarchy and we are getting an issue where workflow ends in error, when we retry its goes through fine. Seems issue is happening only in run time.

Below is the procedure called in node where failure happens. We dont see any issue with query as when retried its fetching records and going further. Iam not sure if it has to do something with p_funcmode.  Any hint on what could be the cause would be appreciated.

IF (p_funcmode = 'RUN')

      THEN

         l_num_quote_number      := wf_engine.getitemuserkey (itemtype => p_itemtype, itemkey => p_itemkey);