Is there a solution for this?

I just opened Firefox for the first time in a couple of weeks and am experiencing the same problem. I see my Gmail inbox briefly before being redirected to the calendar. Clicking the back button produces the same result.

Very frustrating.

Yes that is exactly what has been happening for a month now. HAve you gotten it to fix itself?

After further searching I found a fix for this problem. Click on Tools > Integrated Gmail > remove Calendar from "Element Selection". Unfortunately, it seems that you must do this after each Firefox update. But, it works.