A critical control should block progress when skipping it would expose someone to a fatal risk, like proceeding with confined space entry without a gas test or starting work before an isolation is verified. In those cases the next step should stay locked until the control is recorded as done.
Blocking every step is a mistake, though, since operators will find workarounds if the system stops them for things that do not need it. The best approach is to block only the small number of controls that genuinely prevent fatal outcomes, with a clear and recorded way to escalate when the control truly cannot be done as written.