I have worked on core drillls but never to that depth. The biggest problem I have every had was not with the drill other than the jaws not holding the weight of the rod but with the pumps that could not pump enough preasure to bring the cuttings to the surface and settling back down and freezing up the rods in the hole. Some of the problem was overcome with the bentonite slurrys suspending the cuttings longer but 2km is a feat I wouldn't want the responsibility of. Everything works fine usualy unless you hit a void that takes your mud and if you are not quick you can lose the steel prety fast. Wedging a hole I have never done but to me that too would add more circulation problems. Still even when I drilled difficult holes it was a learning curve that with the loss of a hole teaching everybody real fast for the next attempt. Labs and their problems I know nothing about but equipment upgrades is done all the time in new challenging discoveries as every location is always different.