matt on 22 Sep, 2018 03:05 AM
At the beginning of the summer, I ran into this and filed a bug with Google (the issue is Google Maps not firing the event). They closed the issue as not reproducible, and I couldn't find another mac that had the issue, so I assumed it was a quirk of my machine and moved on. I did freeze the Google Maps API version I was using, which fixed the issue until 4-6 weeks ago when they stopped supporting the old version.
Recently found one other person with the issue, and now you, so I know it's not unique to my machine. Based on that I'm going to check with them again, but it's out of my hands without a bugfix on their end.
View from here and a number of the other right-click options should still be accessible using the measure menu at the top of the screen.