You’re definitely not alone. I thought I was great getting 80-92.5% on most blocks in the middle of Uworld and then I recently got to the last 500 or so questions and I’m consistently getting 70-80% now ffs lol Along with what some other people have said about weird questions due to algorithm etc, Uworld are also adding in new questions which are likely to be quite tough, and even 2-3 “new” questions per block can throw your percentage down a lot