I was having the having the same problem apparently while your doing skills/casting spells you cant swap between bars anymore im not sure if they did it deliberately or if its just a problem from new patch they didn't notice. i doubt they would decide 8 months after the game started to just change up everybody's controls but it was very frustrating i literally had to turn the game off cuz i just was watching my hotbar and clicking 6-7x to swap between them instead of paying attention to fights which is completely ridiculous .