oh and note about "Then, just yesterday, I found out there was another policy called "Startup policy processing wait time" under Computer Configuration\Administrative Templates\System\Group Policy node. I set it to 50 seconds for testing."

this is longer by default.
if you actually use start up scripts or if your logonscript actually does something important, setting it to something realistic like 10 minutes would be advisable. I have even had environments where the timeout has been disabled.
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