listitem updates column randomly

Hi

I have list with two columns

name as  title and UserName as person or Group field.

I am updating the list from custom timer job.

I am getiing all the usernames and user login names in the Dictonary object in key-value pair.

But when i am updating these values in list its updating wrong UserName to wrong name

like

user1 -- User_name45

user2 -- User_name1

user3 -- user_name5

user4 -- No value

It should be like this-

user1 -- User_name1

user2 -- User_name1

user3 -- user_name3

user4 --  user_name4

I am not understanding if I am getting proper data in dictonary why its not updating in the list properly.

below is my code,

if (collListItemUser.Count > 1)
{                      
                      SPSecurity.RunWithElevatedPrivileges(delegate()
{
 using (SPSite ElevatedSite = new SPSite(spSiteURL))
{
using (SPWeb oSPMyWeb = ElevatedSite.OpenWeb())
{
                                  oSPMyWeb.AllowUnsafeUpdates = true;
 SPList oSPListUsers = oSPMyWeb.Lists["UserList"];
 SPListItemCollection oSPListItemCollectionUser;
                                  oSPListItemCollectionUser = oSPListUsers.Items;

oSPMyWeb.AllowUnsafeUpdates = true;


Dictionary<string, string> userList = new Dictionary<string, string>();
foreach (ListItem oclistItem in collListItemUser)
{
string uName = oclistItem["Title"].ToString().Trim();
if (oclistItem["UserName"] != null)
{
                                          Microsoft.SharePoint.Client.FieldUserValue[] userValue = oclistItem["UserName"] as Microsoft.SharePoint.Client.FieldUserValue[];
int userID = 0;
string userlogin = string.Empty;
string userIDLoginName = string.Empty;
bool getCCUserExc = false;
try
{
String strUserName = serValue[0].LookupValue.ToString();
 User oUser = clientContext.Web.EnsureUser(strUserName);
                                                clientContext.Load(oUser);
                                                clientContext.ExecuteQuery();
 userID = oUser.Id;
                                                userlogin = oUser.LoginName;
                                                userIDLoginName = userID.ToString() + ";#" + userlogin;
 if (!userList.ContainsValue(userIDLoginName))
 {
                                                    userList.Add(uName, userIDLoginName);
 }
 }
catch (Exception ex)
{
                                                getCCUserExc = true;
 }
 if (getCCUserExc)
 {
string userLogin = userValue[0].LookupId.ToString()+";#" + userValue[0].LookupValue;
                                                userList.Add(uName,userLogin);
 }                                                
}
 }
foreach (KeyValuePair<string, string> entry in userList)
 {
 try
{
SPListItem oSPListItemUser= SPListUsers.Items.Add();                                          
                                          oSPListItemUser["Title"] = entry.Key;
                                          oSPListItemUser["UserName"] = entry.Value;
                                          oSPListItemUser.Update();
}
catch (Exception e)
{ 

}
 }
                                 
                                  oSPMyWeb.AllowUnsafeUpdates = false;
}

}
});
}

This code is not showing any error but updating the data wrongly.

Anybody got this type of issue before please suggest what wrong here.