When I entered that sequence of moves all at once, I got the same error. Then I entered each move separately and still got the same error. So, I took back the last move and found another legal move, which worked out. A little later, I tested other moves by the E and e pieces, and when I moved the other E piece, though not an e piece, I got the same error. Taking back that move and trying E again later, I got the error "g4 is empty". There seems to be something wrong with the E piece, but I am too unfamiliar with the workings of this generated code to debug it.
When I entered that sequence of moves all at once, I got the same error. Then I entered each move separately and still got the same error. So, I took back the last move and found another legal move, which worked out. A little later, I tested other moves by the E and e pieces, and when I moved the other E piece, though not an e piece, I got the same error. Taking back that move and trying E again later, I got the error "g4 is empty". There seems to be something wrong with the E piece, but I am too unfamiliar with the workings of this generated code to debug it.