No, they're not at work outside of work hours.

I don't think so because it happens outside of work hours too. It's all very random and happens at random times of the day; sometimes in the middle of a shift, sometimes in the middle of the night.

Sorry for the very late reply, I haven't been able to play the game in a while. What I mean is that while my sim is at work, or sometimes between shifts, their coworkers/boss will be randomly removed from the relationship panel as coworkers and I can't use the tones to interact with them. They will be randomly re-added as coworkers later only to randomly be removed again. Like, for example, my sim has 3 coworkers and a boss; the boss and 2 coworkers will randomly disappear from the panel then several hours later 1 coworker will be re-added, then they'll all disappear, then maybe just the boss will come back. It repeats this every couple of hours with a random result on who'll be re-added or disappeared. There's no rhyme or reason to it. I know the sims are still employed in the career because if I go to the friends tab in the relationship panel, I can see those sims (if they're friends) and it shows that their career is the same, they're just no longer "coworkers". If I make the sims active, I can see that their career is unchanged.

I've been having a problem where when I have awesomemod and Nraas mods together my sim's coworkers all end up detagged as coworkers/boss. They're still employed in the career, they just don't show up in the coworkers tab in the relationship panel and can't be interacted with with the tones (like chat with coworkers, suck up to boss). I removed awesomemod and the problem went away but I've never played without awesomemod before so I put it back and went back to testing for a solution while posting for help on the NRaas boards. Now, my game won't load at all without awesomemod in; the game stays at the initial loading screen with 0% progress indefinitely and when I close the game with task manager I get an error message that says something about the "the memory could not be read".

ETA: Sorry, the loading crash was caused by Tiny UI Fix not being updated to exclude awesomemod in it's patch, so you can disregard that part of my post.

ETA 2: I removed all mods except awesomemod, the Nraas mods, the cc for the world I'm playing, and the Smooth Patch and tested a save where my sim has just gotten a job but has not been to work yet. With awesomemod in the sim has two coworkers and no boss, with awesomemod removed the sim has one coworker and a boss. Wtih both awesomemod and Nraas mods removed I have two coworkers and one boss. I think there's something about the way awesomemod is interacting with Nraas mods regarding coworkers that's causing this. I don't know which mod is acting up so I'm posting on both sites.