It seems Wix-Location - Passing Query [arguments/parameters] has got broken between yesterday and today (23 Oct 2019).
From the API:
" How do I pass the query from a page's URL on to the next page I direct the browser to?
If you're directing the browser to another page within your site, the query from the current page's URL will automatically be appended to the next page you direct the browser to using the to() function."
This no longer seems to be working. I've tried creating a test page and it doesn't work. Would someone be kind enough to test it out and say whether it is working or not?