so they best have a plan B
Absolutely. It's happened twice to me. Once after takeoff, due to a mud-dauber wasp's nest in the pitot. I had forgotten to check the ASI during the takeoff roll.
Once due to rain water in the system - and a water-ballasted Open class glider behind me. I elected to continue the takeoff rather than risk having the glider run into me, if I aborted.