gpupdate
atualiza a política de grupo com novas revisões. Veja a documentação :
Refreshes local and Active Directory-based Group Policy settings, including security settings.
/force
também reaplica configurações antigas
/force : Ignores all processing optimizations and reapplies all settings.
Presumivelmente caso essas otimizações tenham estragado algo.
So which one should I use? 99% of the time, you should only run gpupdate. If you just edited a GPO and want to see results immediately, running gpupdate will do the trick. In fact, running GPUPdate /force on a large number of computers can be damaging to your career. This is because these machines will hit a domain controller and reevaluate every GPO applicable to them.