Do you mean the “Countertop Wizard” or the countertops and trims tool? I’ve had issues with the “Countertop Wizard” numerous times over the past few years, on multiple machines and multiple installs, with versions 9, 10 and 11.
For me, it would crash 20-20 when I tried to add a sink in the sink dialog page. If I made the top without a sink, it would work.
Some of the times this happened, I could make it stop by reinstalling the sample-counters catalog, since that’s where the sinks used by the wizard are from. Most recently, that didn’t help. I completely uninstalled and reinstalled 20-20, and it went away.