Different physics after build

I don’t know if I am somehow building incorrectly, but when I run my multiplayer game in JMonkeyEngine SDK it works as intended, but when I run the built game, other players don’t move. If there is one player using the built version of the game, and another player using the SDK version, both fail to run as expected, but when both play the SDK version, it runs as expected. So I think that it is something to do with the built version.

Well did you check the error output? If something actually goes wrong its in there. Typical things would be models that are not j3o, which are not included in the distribution by default, trying to access files in the assets folder which doesn’t exist in a deployed app etc. Otherwise I can only guess. If its like you say without any error messages then its probably a timing/threading issue where when the application is run in the SDK the timing is different such that the bug (in your code) doesn’t appear.