Uhm, I am not sure why this happened to you. At first I thought that the "excluding unused files" option may have cut down the Bodyslam effect file (one of the frost bear moves), but it is there, in the effect folder, everything looks fine. I tried to play from the browser and I could not replicate the error. The bear's bodyslam move executes without problems.
Could that have been a glitch in the HTML5 player of itch.io I wonder?