How to disable "right click acting as left click"
You're clicking for too long. 


Short click &amp; the menu will wait for another distinct click.  
Click &amp; hold &amp; it will trigger as soon as you let go.


If your mouse has a dodgy button, it may let go before you think you did, causing behaviour 2.

With behaviour 1, you can just take your time wandering around sub menus without having to click anything until you're completely ready. The menu will just wait for you.