About assigning the role, how do you assign the bartender roles to existing premade sims? Normally, we can't just add a trait to make them being NPC Bartender for each lot (Unless you use mods such as Zero's one or NPCC, which I haven't tried yet). Having mods make the outcome different, so I want to know your game mechanics before going deeper.
Also, having or not having Get Famous EP will affect the rule of NPC generating, too. If you have Get Famous, the game will pick existing Sims for NPC jobs instead of creating new townies.
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Not only that, bartender outside "Bar, Nightclub, and Lounge" can't keep the role. Their role/job will be removed after you close the game and reload again.
For example, if you visited a Karaoke bar, exited the game to the main menu, and reloaded the game again, you will see that the existing bartender will lose the mixologist title (red font), and the new bartender will come to replace.
Most of the lots that need to have a bar but can't keep a permanent shift are in San Myshuno, or "City Living" lots. Ex, Karaoke bar, Art center. It's impossible to keep the same bartender working there. So, if you visit those lots a lot, you will have plenty of new bartenders who will lose the jobs after you close the game.
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About Living Statue, I haven't had the new one for a long time. In my main save, I have two of them. The first one is a teen guy, and the second one is a young adult girl. The second one appeared more often, but sometimes the first one still appears, too.
What I suspect is, the game will make new NPC when the first one isn't available. For example, if this red shirt guy visited the lot as a normal person, but then the game needs a Living Statue, it will make the 2nd one. But... the game will prefer to use "the recent one" instead of being completely random.
So, if you want the red shirt guy to appear as Living Statue again, you may remove Living Statue trait from two new ones (aka, remove the role), or delete them if you don't want to keep them in your game. Then wait to see if the red shirt guy can do a living statue job or if the game still makes the new one.
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I can't prove the result, because the game seems to change the mechanics of townies generating after Enchanted by Nature EP.
I used a lot of mods to stop townies from generating, so I can know when the new case happens without my consent.