Firebase: escaping characters in redirect

I have a project running for over a year in Firebase. It has a firebase.json with the following redirect:

"redirects": [ {
      "source" : "/single-reports/:id*",
      "destination" : "/dashboard/#!/single-reports/:id",
      "type" : 302
    }],

However, suddenly some clients started to complain of an error. I went to check and the url is being redirected to

/dashboard/%23%21/single-reports/-LMnXAtEzTQQzffY0Bfy

I didn't touch anything. What might have happened? How to fix?