This is one of those things that happen when a site doesn't have a lot of people using the system so they "live" with little inaccuracies but once people start looking they aren't as good about these things
For instance in the season manager and product guide we have when the BO/Tickting folks update the Synopsis for the shows they change for all the past shows in earlier FY years. We are told all the ticket info stays the same but the synopsis can't.
Example we have a Musical Season each year with 3 musicals. So when Musical Season 2019-2020 is loaded into the system the synopsis for seasons 2017-2018 and 2018-2019 now show the synopsis for 2019-2020.
Does this have to happen? Is it happening because the base set up is somethng like Prg 1, Prg 2, Prg 3 and then synopsis is refreshed each year.
I get how this started but it is hard getting folks to feel comfortable with system it we have to keep explaining why things appear wrong.
What you're experiencing is a holdover from the initial design of Tessitura's Ticketing Setup for use at the Metropolitan Opera. The idea of Title/Production/Production Season/Performance is that a Title represents a piece in the operatic repertoire, i.e. "Turandot" by Giacomo Puccini. Puccini's Turandot is always going to have the same basic synopsis. The Production level represents a specific designer's production of one of those opera Titles, i.e. "Franco Zeffirelli's Turandot". Naturally, a production might tweak the synopsis a tiny bit, so when a new production is created it makes a copy of the synopsis from the Title level, and then can be further tweaked. But from now until the end of time, every time the Met mounts Zeffirelli's Turandot, the synopsis is going to be the same, so in Tessitura it applies to every production season and performance that appears below that production level.
What's happening here is that your box office (like pretty much every box office that isn't for an opera company) is using the Title and Production levels of this hierarchy to mean something other than an opera title and opera production. Production is probably indicating a recurring part of your season, like "Musical", the content of which changes every single year.
So, synopsis just isn't the right place to store data like this if you want it to be historically relevant. A content type that can be applied on the Prod Season or Performance level would likely be a better choice, but this won't necessarily be surfaced in the application in the same places that the Synopsis would be.
This is absolutely an area where the Tessitura application needs to innovate a bit since the majority of us are not opera companies. I've submitted enhancement requests on this in the past, and you can certainly do the same.