If it were going the other way, I would say it was Norton. Because Norton would be trying to protect you and having a long timeout might leave you "vulnerable". I still think it's Norton and not just because I hate antivirus apps because let's be honest do you need antivirus on an Android, not typically, but whatever. That doesn't seem like something any of the other apps would care about. If you don't want to uninstall Norton, try just clearing the cache and/or the data, force stopping the app and restarting your phone. There might just be something stuck in it. If that fails then try uninstalling it.
In the meantime do you have it set to lock immediately when the screen is put to sleep? This overrides 30 seconds and 10 minutes. Unless you're the type to close your phone and immediately open it again or the type that sits your phone down screen on and just expect it to close and lock when you look away, the immediate lock option is the way to go. Personally I set my timeout to 10 minutes because I'm the type that gets distracted or finds the one app that doesn't keep the phone open while I'm using it and gets frustrated if the screen times out just because I looked away. That's actually the first setting I change on a new device because there's always waiting in the set-up process and the phone screen timing out after every step is too much.
Long way round, it's Norton if it's any of them.
Not sure how well you know Tasker but you might go the tasker.wiki.com and search for screen timeout. I know there are some settings that it can't do, like I want it to turn off my device, or close an app and it can't do that.
Best wishes
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