So I've been exploring Op.10 No.1, not really intending to perform it but interested in the technique. One of the hardest arpeggios I found was the A major, particularly ascending and the major 3rd of A-C# between the 4th and 5th fingers was really difficult. Having a play around with it today, doing a whole bunch of repetitions and not really improving. Then the quote "Insanity is doing the same thing over and over again and expecting a different result," popped into my head so I decided to do things differently physically. I had no idea where to start so I just did weird and extreme and (in my mind) suboptimal stuff - extreme pronation and supination were a part of this.
Having done this for a few minutes I accidentally stumbled upon an extremely effective movement. When playing the 4th finger, slide towards the fallboard. I can tell you it was a eureka moment. The awkward gap between 4th and 5th no longer existed and it started to feel fluent. Then I looked at Nahre Sol's video about this and of course she is doing it but says absolutely nothing about this crucial slide.
The next challenge is doing this arpeggio descending. Wish me luck.
Is this the one you are talking about? Imigur link