I was once sabotage by a rival site and my google ad was temporary disable due to copyright files. but recently i change the domain and instate the google ads again , then google found out again that i serve the ads on the site again. is it due to google periodically checking or someone reporting. thanks, regards
If you are ranking good and basically giving hard time to your competitors - could be reporting, otherwise checking...
Just remove the stuff for which you think you are getting your site banned. You may not be third time 'lucky'..