From my limited experience with programming, it looks like both jumping and stompable have some old code or something, possibly from an outdated version I kept reading about.
When you run into these errors, click the button that says "open all" and it should bring you to the GUI of the blocks of snap code. (on two separate tabs) For me, the "dolater" piece was red. I swapped that out with the "do after" instead (under the time category on the right navigation pane) but kept the times the same; worked fine in flash player after that.
