more discussion with teacher
1) there are two sets of mode 5 and 5.1. The first set is wrong and need to be removed. Thanks.
[color=blue][b]already solved [/b][/color]
2) the sim still hangs after a while. This bug will affect the pace of learning if it is not resolved. :)
[color=blue][b]already solved by compiling in EJS4.3.5[/b][/color]