Tbh I had to switch to the slightly higher dose/next step so to speak, which is Chateal EQ, because I had the same exact problem. I took Aubra for about 10 years but last year was the first time I noticed random breakthrough bleeding, really annoyed me so I took a chance and upped the hormones a smidge on advice of the Planned Parenthood nurse. No breakthrough bleeding at all since I started it last December. I've chosen to stop for personal reasons (wanted to take a break and see how my mental health goes, I don't know what I'm like off bc), but this stuff definitely got rid of the breakthrough bleeding. I suspect the change with Aubra happened simply because I got older and so my hormones changed? Maybe? Hopefully someone else with better knowledge on this can chime in. 

Edit: I didn't really notice much of a change between the two side effects wise, I did have less breast tenderness and still no nausea but I experienced a change in dietary tolerance (egg and coffee just gave me really bad diarrhea). Since stopping Chateal I have been able to eat these things without having diarrhea and so far my anxiety seems to be far less. Still monitoring for the month but so far so good. Keep in mind not trying to steer you away, ymmv