I just finished comparing files with winmerge:
v6.0-untouched vs v6.0.1-untouched -> no indication of null detector
v6.0-nulled vs v6.0.1-nulled -> no indication of null detector
today after that guy complained, I test my signup page and get 404 error.
Downgrade to v6.0 signup is fine again.
Update to v6.0.1 Sign Up is working perfectly FINE.
So, the nulled files fixed it.
If anyone having this problem, just update using the same version or v6.0. updating will refresh/delete whatever the author did through backdoor access to QuickQR.
I am guessing the "nulled detector" (if there is one) doing its job manually, it's like a remote backdoor by the author. Messing/blocking the signup process.
It is a coincident that this happen right after that guy complained LOL! Making me suspect that he is the author even more.