TaoXie Unfortunately, it is difficult to pinpoint the cause with the information provided, but from what I have been able to find, it seems to run slower when Enable Audio Scrubbing
is enabled in the Timeline Settings, or slower depending on the preview settings.
If it is slow to click regardless of these settings, could you please create a new Unity project to create a minimal Unity project that can reproduce this problem and then email it to us?: contact@esotericsoftware.com
Please include the URL of this forum thread in the email so we know the context. Then we can take a look at what's wrong.