Pico Unicorn pack needs power cycling often

I am working on the Pico Unicorn pack using micro python, with some animations. However, I am finding that every three or four download and stop clicks, the system sort of hangs and will not go again until I power cycle the Pico.
Is anyone else seeing this?
This happens when programming both on the Raspberry Pi and the Mac. I am guessing that something doesn’t like being shut down arbitrarily and is causing a crash somewhere. Is there a way of stopping the Unicorn library as I feel this might mitigate the situation. Or is it something else?

Sounds like this might be a similar issue to the one described here?.