For example, all the ores render as themselves temporarily, but suddenly become copper blocks only on the server,

Or limestone areas render like this, it only happens on the server not the singleplayer worlds I have tried and even imported to the server.

Its purely visual as mining them is ok.

Edit: every single block renders the wrong way from the mod, this seems like an issue, it only happens in the server not in singleplayer

Please make sure the server is using the exact same version of Create as you are