I have this issue too. I tried a lot of settings, but nothing changed. I have disabled all extensions, but nothing changed. I wrote to the bug report, but nothing happend.
Under such circumstances I would change the browser. But unfortunately I have so much login data and form data saved in Opera and all the histories. To rebuild that in another browser costs me hours. And I use the VPN a lot.
The hope, the other day the problem will be fixed, lets me stay with Opera, at this point. But that's driving me crazy, since I use the browser the whole day for business applications.

I have downgraded to Opera 77.0.4054.90 https://get.geo.opera.com/pub/opera/desktop/77.0.4054.90/win/

I have downgraded to this version. But you have to disable the automatic download/update. This worked for me https://forums.opera.com/topic/36333/solved-how-to-turn-off-auto-update

To get rid of something, which is a feature, may be a workaround, but no solution. BTW: I dont have a combined bar, but the problem. I also dont have an AERO theme, but have the problem. I am already testing other browser like Vivaldi and Brave.

Meanwhile Version 79, but bug is still there.

Searchbar issue here with Win 7, SP1 Professional

My Opera did yesterday an Update accidentally. It only lasted 2 minutes and I had bug again. I immediately switched back.

I have downgraded to Opera 77.0.4054.90 https://get.geo.opera.com/pub/opera/desktop/77.0.4054.90/win/

I have downgraded to this version. But you have to disable the automatic download/update. This worked for me https://forums.opera.com/topic/36333/solved-how-to-turn-off-auto-update

I have this issue too. I tried a lot of settings, but nothing changed. I have disabled all extensions, but nothing changed. I wrote to the bug report, but nothing happend.
Under such circumstances I would change the browser. But unfortunately I have so much login data and form data saved in Opera and all the histories. To rebuild that in another browser costs me hours. And I use the VPN a lot.
The hope, the other day the problem will be fixed, lets me stay with Opera, at this point. But that's driving me crazy, since I use the browser the whole day for business applications.