You just might have a very unoptimized original order, with page break properties set on start/end of group. For example, if your database stores records for 'country' in this order:
Canada
Canada
USA
Canada
USA
Canada
USA
Then with specific order "USA", "Canada", you'd have only 2 groups. With original order, however, you'd have 6 groups. Since the group is changing on (almost) every record, it might seem like it's "looping" over the values, repeating them again.
If you don't want it to do this, you can either (a) not use original order, or (b) change your source data to be better organized.