After some testing, I can't find any way to fix it on my end, the problem seems to stem from the class change and how it interacts with highfive's taunt choosing.
The highfive looks for class, model, and team. But those should change when the class is set.
I can't tell whether it's a prblem with mine or the highfive, but somewhere along the line, it's having problems getting a correct value.
I get this in the console when the random civilian models appear:
Dynamic prop prop_dynamic:no sequence named:taunt_hifiveFailFull (or whichever taunt the highfive chooses)
Suffice to say, I can't figure out how to fix it, sorry.