Analysis board: mastery difficulty computer won't move if there is cloud analysis

I opened the analysis board, clicked the 'Practice with computer' button and toggled to mastery difficulty. I made a move, and after the fixed search time, the computer didn't make a move. I tested different positions which had cloud analysis, different engine configurations, and even on different devices, the bug still occured. Interestingly, the bug didn't occur when I tested positions which didn't have cloud analysis or casual difficulty computer. Why does this bug occur in later versions of Lichess? The bug didn't occur in older versions, did it? 

It's a pretty recent bug. Thanks for digging into it! It has been fixed and that fix should be deployed in a few days time.