Now I need answers from the staff around this topic and how and what you are checking when you give a theme OK.
I´m sitting right now with the 6th theme in short time that is SO full of bugs and bad documentation that I need to check what the criterias are for a theme to get away with this and pass to us buyers…
So please, I´m really really tired of spending time and money on items that is not working 100%!
Hey @Pontus!
All items that are available on the Envato Marketplaces go through a review process by quality workers (they’re human real-workers and as humans we all make mistakes from time to time, but hey! that’s life) and then they determine if it is suitable to be available for the marketplace to ensure the item works as it states and also ensuring all the functionality is up to a professional standard.
The good thing for buyers is that all themes available on the Envato Marketplace have a demo online which you can test and trial out some functionality alongside this some authors of the community even make their documentation publicly available - which is great as you can see the nitty gritty details!
The first option I would recommend you do is check if the author supports their item and if they do if you contact them through the “Support” tab on the item page they will be able to assist you in the best possible manner and give you the most accurate results.
However, if you believe the item does not function as it states on the item page with the incorrect functionality if you contact the Help Team they will be able to issue you with a possible refund and help solve any problems.
I hope this helps and good luck! 
To be honest, I really do not agree with most of the terms especially in case of themeforest. A single product is being reviewed by different checkers. Again Themeforest design means to me having big fonts and big spaces between sections. Sometimes, I found all the things don’t event work properly. Some designs I found really at 0 level and still being approved. And finally all the designs are almost same. I have worked as a freelancer more than 10+ years and I had to change the designs and codes for the clients every time. I highly doubt the quality of some checkers.