There is a reported bug in a recent/latest version of the Discourse software, on which this forum runs whereby some users’ (Unread) post count is incorrect… I have it too: my ‘Unread’ shows ‘1’; but everything is in fact read.
Additionally, as @Suedkiez has already reported, I have been getting notifications of likes and solutions made in response to posts that have nothing to do with me - not the post or even the thread.
I have since come to the conclusion that these might be solution notifications for every solved thread I’ve posted in, even if the solution was not mine. Which might not be the worst thing. (These solutions are not attributed to me in the solution list of my account).
I don’t think I received likes that weren’t for me.
FWIW on another forum running Discourse I tried logging out and in again.
Did not solve what - in that case - was the opposite, or at least a ‘variation’ on the reported bug I linked to in my OP: counts not or erratically updating.