It happens randomply like once a week or so. Sometimes after a fresh restart of Opera and/or Windows, sometimes after Operat has already been running for days. I cannot reproduce it. In rare occasions I can fix it by clicking the reload button on the top left. Closing and restarting Opera may or may not fix the problem.

I haven't noticed the issue with the Twitter sidebar.

Any ideas how to solve the issue or pinpoint the cause? Especially, as the error only occurs occasionally, I'm not sure what of the things I tried, did or did not resolve it.

Opera 70.0.3728.189 (but has been the same for many previous versions)
Windows 10 home 1909