Note: TM2 support for .op Plugins is in the works but not there yet so don't update this if you use it for TM2!
Here's a solution for the "Joinbug" in the new game, also known in the form of "Please Wait..." in TM2!
With this plugin, you can force-rejoin the current server you are on by selecting the item in the Openplanet overlay menu.
You just need to put the contents of the zip archive in your OpenplanetNext / Openplanet4 Scripts folder and you are good to go. You will find the button in the "Scripts" menu of the overlay.