I had issues when purchasing my season ticket as I also have a kids one. It would only let me renew one and then told me that I couldn't do the kids one unless I also bought an adults one. Teething problems with new system I imagine. Contacted the club and was sorted quickly. My season tickets have designated section, row and seat number on them. I also still have the reserved sticker on the seat from a bygone era. Completely agree that these should be removed from non reserved seats and updated for current seat holders.
I had the idea that all stand season ticket holder would have an allocated seat but clearly not the case. For 99% of games it is not an issue but for bigger games with a larger crowd they should be able to sit in the seat they sit on for the rest of the season.