You have to turn off normal WC3 syntax, but turn on the better, enhanced syntax checker for jassnewgen. With it on, it will only report the actual errors, and not the errors caused my new content that it does not know. Even with syntax checker on, no errors should happen and if they do, then eithor he did something wrong, or you imported them incorrectly.
Remember, all it takes is one wrong piece of code to cause the map to not load properly, it may still run but not easily.