I just discovered that when you set a walk-in path thickness were no separate deboarding path is selected, the passengerpaththickness_deboarding = is not set to the value of the boarding path thickness. You need to enable the separate deboarding path to set it for deboarding as well, or change it in the .ini
It would be great if the editor could be updated so when you set a thickness for boarding, it automatically sets the same thickness for passengerpaththickness_deboarding = when separate deboarding path is disabled.