I noticed the "Unlock on Secure Desktop" button, and thought it will work as that it will identify my windows PC as secure desktop and I don't need to unlock 1Password so frequently. And in the Preference, Browsers tab, I tick the "Unlock on Secure Desktop" tick box. Next time I try to unlock 1Password, the unlock screen goes to full screen. But then the problem comes - I cannot unlock. The full screen disappears when I'm still entering password. I haven't fully entered my master password and it quit. Then I cannot open my 1Password at all. I click on the 1Password icon and the menu won't appear. Also my Firefox browser 1Password icon won't react when I click. I have to go to Windows Task Manager to kill 1Password processes, then restart. It will bring me to full screen again, and it enters a vicious loop. Until one time, I enter my master password very fast and the full screen didn't quit yet, then I unlock my 1Password. And I untick the "Unlock on Secure Desktop" tick box in Preference, then I don't have this problem any more.
Attached is my diagnosis report. This definitely looks like to be a stability bug to me. It just didn't work well. Hope it can be fixed soon(though I might not use this function any more, didn't find what's the point of using it yet).
I have sent the diagnosis report to AgileBits support. But thought posting on the forum will help ppl who might meet similar situation as me.