There seems to have been a slight but noticeable uptick in users reporting that banners are not being properly suppressed after being dismissed, most recently by @Romaine .
The issue seems to not to be limited to any one particular banner and doesn't seem to be being caused by clearing session data/localstorage/cookies.
There have been a large number of new banners created with new code and shown to large populations of the community. There may be some sort of unknown issue being caused by either the banner itself or that there is a minor and difficult to replicate software issue that's being revealed from the large footprint CN is having on the community over the last few months.
This task is to track, monitor and try to explain what may be causing this increase in reports.