It means your version of a model is different than the version of the server, and thus gives errors.
If you go to your Blockland folder and delete "cache.db", it will have to redownload the newer version from the server and solve your problem.
Keep in mind that this will cause you to redownload everything again, so loading times may be long again for servers you joined before.
An other way is to find a version of that "vehicle_tiger1" vehicle and put it in your addons.
Although I am not sure this will help.