My $0.02...
My experience has been similar: problem tolerated for months, went away for a few, then returned several months ago & remained. Signed out, cleared the cache, removed & reinstalled the app, but nothing would remove it for longer than half an hour or so.
About two weeks ago, I bought a new phone directly from Motorola -- Android 10, even. Latest version of the app was installed during set-up, I signed in, and - boom - new souvenir notification was STILL active. I signed out then back in, but it stuck. I've given up trying to clear it.