Thanks @hellonearthis for that fix, that i will use! It eliminates as well the PNG export error.
To summarise at this point:
Both Vega lite and Observable teams use different encodings to set xmlns attributes in the SVG, in the end, they pile up, which causes the reopening issue.
No matter which encoding process is the most academic, it would just be appropriate for both parties to agree on the same.
I don’t know how I can help with this, except to relay this analysis on vega-lite-api github, so do i…