Sorry for the delayed response, I must've missed the topic.
If it only happens in LAN, then there is no fix right now, you'll have to wait for the next core update. If it happens online as well, then make sure you have the latest version, it should be "beta 3" for Mac (you can see what you have in the main screen of the game above the `Online` button). If you don't have "1.034.0 (beta 3)", then redownload and re-install the game. You can copy/paste to backup/transfer your decks, textures, etc, to the new installation.