Why do I see spikes and boundaries "fly" off the model after applying a NURBS Surface?

A model that is very small usually causes this issue. To check if your units are correct you can use the Measure Distance command in the Analysis tab.

You can also change the scale of the model in Tools>Modify>Scale.

In the Scale dialog box enter an appropriate number and select the Origin option.

Another option is to reopen the model with the correct units.