The most noticeable scoring controversies involved Canadians to be honest. Americans won medals regularly and golds at that. Against Russians. Canadians were blocked from podiums because of the old horse trading that use to happen. I remember watching the ice dance at Salt Lake and seeing the Canadian pair skate an amazing free dance, until the very end when the final movement had a problem. Commentator just went, and there is the excuse to keep them off the podium. It was always hilarious that Canadians medaled and won championships at Worlds and Grand Prix final only to skate the same at the Olympics and not medal.
As for judging now. Most of the biggest controversies have been in the park events of skiing and snowboarding. People connected with the X Games being completely dumbfounded by some of the results at every Olympics since park events were added.