Just got my first cube and have been following Pogobat's instructional videos on youtube. I've done about 10 solves so far but I just hit a wall on my latest. I'm doing the final (top) layer...i have done the cross, lined the middles up, and now I'm trying to place the final corners with the algorithm: U R Ui Li U Ri Ui L - but it's stuck in a loop of 2 always being correctly placed and 2 always being incorrectly placed (they seem to be opposite each other). I've done said algorithm again and again - starting with a correctly placed corner in the bottom right as pogobat suggests - and also with an incorrect corner in the bottom right to try and mix them back up or something...but it won't correct itself. Any suggestions would be wonderful!