Table or view not exists error from procedure - occurs randomly

Question

I have a procedure used in a website, it works fine until recently we occationaly getting an error said Table or View not exists, the error will go away if refresh the page which will re-execute the procedure.
This procedure uses an table object as temp table and just a select statement form several tables. The table object is used in other procedures as well. I can't find out what cause this error because it's not always repeatable and the error message didn't give out the exact table that cause the error.
Any idea what might cause this or how to trace the reason that cause the error?
We don't have a good DBA here so really need some help, any advice are welcome.
Cheers

Answer 1

I don't think it's possible that any previlege changes are made or the tables in used in the procedure are droped because after we run our db scripts to build the db, then we testing the website which can only execute procedures, and no procedures execute DDL script to make such changes.
It's worth to mention that we have a Table Type called EntityIDTable() which is used in many of our other procedures, but I think table type is initialise as local variable in each procedure so shouldn't conflict to each other, am I right? Also, the same script are running several times a day to generate same db but with different schema names so we can test on different site templates. One change script did drop one of the table and recreate it, but it use the &DB_Schema_Name.Tablename to drop a table so shouldn't affect the table in other schema I think. (I enclosed the procedure below)
Also, any event log in Oracle I can enabled and trace the problem to find out what table is not exists at that point that this problem occurs?
Cheers
Below is the sample code of the procedure:
aEntityIDSet varchar2,
aCount out int
as
L_KeyID Category.CategoryID%type:=null;
l_strEntityIDSet varchar2(255);
l_strPipeSepValsInput varchar2(255);
l_UserEntityID varchar2(255);
l_EndPointInput int;
l_Strlength integer;
l_UserKey NUMBER;
l_UserOriginalKey NUMBER;
l_RREntityData ENTITYIDTABLE:= ENTITYIDTABLE(); /*creating on object from a table type to store entity values in*/
-- end of Local variables used for Category Security
begin
-- Category Security
-- Split up the EntityIDSet
l_strEntityIDSet:= aEntityIDSet;
l_strPipeSepValsInput:= l_strEntityIDSet || '|';
l_EndPointInput:= instr(l_strPipeSepValsInput,'|',1,1);
l_UserEntityID:= SUBSTR(l_strPipeSepValsInput, 1, l_EndPointInput - 1);
l_UserKey:= To_Number(l_UserEntityID);
l_UserOriginalKey:=l_UserKey;
l_strPipeSepValsInput:= SUBSTR(l_strPipeSepValsInput,l_EndPointInput+1);
l_Strlength:=LENGTH(l_strPipeSepValsInput);
While ( l_Strlength > 0) loop
<<get_entityId>>
l_EndPointInput:= instr(l_strPipeSepValsInput,'|',1,1);
l_UserEntityID:= SUBSTR(l_strPipeSepValsInput, 1, l_EndPointInput - 1);
l_UserKey:= To_Number(l_UserEntityID);
l_RREntityData.extend;
l_RREntityData(l_RREntityData.COUNT):= Entityidtype(l_UserKey);
l_strPipeSepValsInput:= SUBSTR(l_strPipeSepValsInput,l_EndPointInput+1);
l_Strlength:=LENGTH(l_strPipeSepValsInput);
end loop get_entityId;
-- the block above used in many other procedures to get the entityID
select Count(Distinct ri.ID) into aCount From
-- here joint to other 6 tables
-- the inner join below use the ENTITYIDTABLE
inner join
(SELECT distinct KC.KnowledgeGeneID FROM Category Cat
     inner join KnowledgeGeneCategory KC on KC.CategoryID=Cat.CategoryID
     where EXISTS (SELECT EntityID FROM TABLE(cast (l_RREntityData as ENTITYIDTABLE)) ET
     INNER JOIN (SELECT EntityID, EntityTypeID, CategoryID FROM CategoryRowLevelSecurity CRLS
     WHERE CRLS.EntityTypeID=1) S ON ET.USERENTITYKEY=S.EntityID
     where S.CategoryID=Cat.CategoryID
     UNION
SELECT EntityID FROM CategoryRowLevelSecurity CRLS
     WHERE EntityID=l_UserOriginalKey
     AND EntityTypeID=0
     AND CRLS.CategoryID=Cat.CategoryID)
     OR NOT EXISTS (SELECT CategoryID FROM CategoryRowLevelSecurity CRLS
     WHERE CRLS.CategoryID=Cat.CategoryID)
) CS ON CS.KnowledgeGeneID = k.KGID
where ri.ProcessID = riPro.ProcessID)
end QueryNotifications;