It's been a while since I share a piston but something I possibly have done is stopping me from seeing the piston import code.
When I try to do an anonymized or snapshot I get a pure white overlay so I can't see the code to allow me to import the piston to my son's account. I can see the page come up with the code but it's only ms and it's gone.
I had a Dark Reader installed in Chrome but I have disabled that to no avail. Tried DuckDuckGo same thing.
I know this isn't your bailiwick @nh.schottfam but I can't remember who does the dev for WebCore UI.
EDIT:
DuckDuckGo Privacy Essentials needs to be disabled as well. I can see the code now! 
