A better Maple they said. Every patch or maintenance, there's always something wrong. God knows what they're doing, just makes things worse than better. Patch took away remote effects (transparent effect is useless can still see people's numbers), Ursus glitched. And now there's lag for maintenance.
To solve this issue:
1.- Use the Chat Channels hotkey and join any channel, that should fix it.
2.- It's possible that the Channel list will not display any channels to select, it can take a while according to some people on reddit. If this is your case, good luck trying to load the channels before the client crashes.
3.- Better stay away from the Cash Shop.
I manage to join a channel and the freezing stopped until I opened the Cash Shop to buy a Teleport Rock. After I got out the game restarted freezing, even when the Chat Channel panel said that I was still on the channel. After I log out the whole client started freezing and I had to restart my laptop. Haven't been capable of re joining a chat channel after that.
Just spam them with tickets and play something else until it gets fixed. Seems to happen at very random times, nothing you can really do about it. Joining chat does help but say you dc(and you will dc since it's maple we're talking about) you may be lagging on login yet again.