before the launcher update (V15?) Blockland worked all fine for me and many others who use osx versions 10.6 or <.
After the launcher update, the downloads form all servers are written in a cache.db file instead of the addons folder (i think). And this is where all the problems began occuring, Random crashes, Sqlite errors and MUCH trouble loading addons with different versions that you have currently installed.
There is some existing solutions for the crashes and sqlite errors, Like deleting cache.db or making it "read-write" over and over again.
But none of these is an actual solution to these problems.
Even tough the cache file is faster to download for the sake of mac players, please do it the old way.