When most people talk about the "gap", they are referring to a gap between selector switch and receiver cover. This gap is created from the selector switch being installed too low on the receiver. Not a big issue.
However, on OOW/ITM Receivers, another gap can sometimes be found. This gap is more serious because either the rear trunnion or something was not put in right, which causes a gap between the back of the cover and the rear of the receiver. A difference of 1/8th of an inch. What this means is that the when the cover is locked in, it can still be moved back and forth. When firing with this gap, the cover can be jarred loose opening up the receiver.
However, Vectors have a 5yr Warranty so its no big deal to fix the major gap, I dont think they will fix the selector gap though? Not sure havent asked.