@Aivars
It's not bound to a particular file, it is _always_ the case. From my experience, as soon a recurring variable or something similar is written, the lag happens because Code Explorer updates the list immediately. And this updates hinder the coding. As far as I can tell, this is mainly happening with PHP code. I can't say I have experienced this in JS (but I'm not writing JS code as fast ) and CSS.
As soon I close the Code Explorer, the lag stops. So, for me, it lloks like the Code Explorer has something to do with it.
Hope this helps a bit.