Hi,
The inverted question mark issue was corrected a few versions back. If you don't have the latest version of the font installed (you can only be sure to get the latest version from this site, or dafont.com) that might be the reason. The reason it's incorrect in the font map is because I haven't bothered to update the image.
If you are sure that you have the latest version installed; in what software are you experiencing the error?
If it's on a webpage that uses google fonts, then obviously it doesn't make a difference that you have the latest version on your computer, as it will just use the version on google's servers.
Anyways, the font should be updated to a new and improved version 3.0 on google fonts in not too long. I just can't tell exactly when as google is not the best at setting unnecessary deadlines for themselves.