The published topic will have a probability that it will not take effect when the user likes it for the first time, and the cancellation of the like will only take effect after the second like. What is the reason for this?
This is the first like, the icon shows that the like is successful, but it does not actually take effect, you need to cancel the like, and the second like will take effect
This is not absolute, there is a probability that the like will be successful, and there is a probability that the like will not take effect
I actually noticed this behaviour here on wpforo.com in a couple of occasions.
There is no such issue in wpForo. The only reason which could cause such issue is the internet connection. When you click the button it sends and get data via AJAX, if the connection is bad it may stop, and you'll not see the result.
Also, this could be hosting, WordPress and browser cache issue.
So there is no such a bug in the plugin. If you've ever seen a single issue here at wpForo.com then it was a temporary internet connection issue from your side or from the wpForo server. When you click it a second time, the connections is updated and retained. The same happens with the cache issues.