This bug was also posted by me in different exposition.
The point is: when topic creator changes something in the topic (category, tag, etc.) - ALL users that “watching” this category or this topic - they all will receive a notification. After user will press on notification - he will be redirected to the first post of that topic.
This causes a problem when you using “telegram notification plugin”. All users will receive first message of the topic again after something changed in it.