@burnout426 Hello, thank you for your answer.
I did what you asked, including a reinstallation of Opera while properly removing my data, but even with a fresh installation, the problem persists. I don't have the RAM limiter enabled, nor any extensions installed.
I'm not sure if it helps, but I didn't have this issue before the latest update.
I tried downgrading to earlier versions, and apparently the problem is the same as well.