My shows are named using ShowName - ssxee - EpName and these are automatically grouped by Show name with the episodes in series and episode number order.
I now have a show with Series 11 and 12 loaded on the iPad, and the ShowName includes the 1 from season number.
The show is listed twice, with differing shows in each group with overlap in episodes. Some Ep's are unplayable from Group 2, yet work from Group 1.
Images are
1. iTunes showing New Tricks Seasons 11 and 12 loaded.
2. TV Shows display from iPad showing 2 groups for New Tricks 1
3. Show view of New Tricks 1 Group 1
4. Show view of New Tricks 1 Group 2