Hash Table (#) Order By Problem With More Records

We have one single hash (#) table, in which we insert data processing
priority wise (after calculating priority).
for. e.g.

Company Product Priority Prod. QtyProd_Plan_Date
C1 P11100
C1 P22 50
C1 P33 30
C2 P11200
C2 P42 40
C2 P53 10

There is a problem when accessing data for usage priority wise.
Problem is as follows:

We want to plan production date as per group (company) sorted order and
priority wise.

==>With less data, it works fine.
==>But when there are more records for e.g. 100000 or more , it changes
the logical order of data

So plan date calculation gets effected.

==Although I have solved this problem with putting identity column and
checking in where condition.

But, I want to know why this problem is coming.

If anybody have come across this similar problem, please let me know
the reason and your solution.

IS IT SQL SERVER PROBLEM?



Thanks & Regards,
T.S.Negi