Currently the joblist is coded to manage jobs with maxnumber > 1 but it doesn't work. It records the name of the slave in the job and if you assign a second slave to the job it removes the old one. Current Strive jobs only have a maxnumber of 1 or unlimited making this a low priority fix but it would help mods.
Ideally if you assign someone to a job that is already at max, it would warn it is full and looks for someone to remove. A new rule is needed for this and it is presumably (a) someone who is not in the mansion (b) first/last worker found in the joblist.