This happens both with the saved tabs that are reopend after Opera Gx start up. I tried many times as an expirement. Press the X on the top right. Start up Opera Gx and the youtube video that was saved will display an advert. Other than that Many comic websites Like Mangakakalot and the like have certain amount of adverts popping up. The adverts do not fully show up as they are shown as gray blank squares butthe shape and the pop up of the advert still manifest interrupting the reading process.