Yes correcting my earlier remark. I should’ve said that that was the ideal situation. It’s probably rarely works out that way, although it might for some divisions at an event.
Yes on the pause in radio calls for an urgent situation. That can mean that several rider- jumps are never reported in.
Sometimes after the issue is cleared, course control will go back and check with each judge about all the fences that missed being called in during the urgent period. But that isn’t required, and it may not be feasible if there is already a lot of current radio traffic.
Also a note that if a jump judge makes a radio call, but was unknowingly talking over another jump judge, they won’t know that nobody heard their radio call. So they don’t have a reason to repeat it.
In general, Course Control will know that they may have missed some radio calls. But they do not always go back and try to get that information.
Control is really there to help manage the flow of riders on course, and to help avoid and/or coordinate the response to hazardous situations for riders. As has been pointed out, they are not official scorekeepers.