Macbook Pro trackpad clicking stops working after rendering

I ran into an issue on a 2018 Macbook Pro where the trackpad click stops working after rendering a sequence or effects, specifically one that contains an Optical Flow 50% slow motion.  I can move the cursor around and I can "option-click" because I have that set up in the lower left corner of the trackpad but standard clicking doesn't work.  The first time this happened, I had to reboot because I couldn't do anything else.  The second time, I had a Magic Mouse handy and was able to get clicking to work again.