Limit of results returned by OCL when requesting updates by OclClient.fetchUpdates is set to 100000 items by default, but the maximum number of items per page imposed by OCL service is actually 1000. We need to do subsequent calls to fetch all remaining items if they exceed 1000 items limit.
You need to append to the query in fetchUpdates: &limit=1000&page=(starts from 1). If there are 1000 returned items, then request the next page and repeat until there are less than 1000 returned items. You need to combine all responses into one OclResponse object and return it from fetchUpdates.