It locks up. I do not know more than that. Often, it happens right after clicking an action. Sometimes it will do the action before locking up, sometimes it will even update things like inventory before locking up, and other times it won't do anything apparent at all--it just stops responding to anything. I may try to play some more and see if there is any pattern to it (I did finally complete a game and escape the island). I also encountered the bug reported by UnitVector in he comments.
Gave it another try. The only thing I am seeing right now are a lot of CORS cross-site scripting errors in the console log with api.gameanalyics.com.
One pattern that seems consistent: Trying to craft consecutively locks up. Doing some other action in between crafting seems to avoid locking up.
Same here : picked berries once, second time it froze. Frozen berries ?
That seems to be he pattern. Doing (almost?) anything twice in a row causes a lockup. I just locked up by chopping wood twice in a row.. Which would have given me enough wood to create the raft and escape after only 17 days. :-(