Since 2.7.3 tcp:close() no longer causes any crashes (even when the socket was already closed), but it seems that the connections are not cleaned up properly yet, possibly when they are closed while still connecting?
There is a limit of opening 2 TCP sockets (with SSL) at the same time, and as long as I only open a new connection after the old one closes (usually by the server), this works without issues. However, when calling tcp:close() quickly after tcp:open() (I'm guessing this is while it's not fully connected yet), it appears to "linger" for a while, and prevents me from opening new connections (error returned just says "Busy"). Eventually a connection can be opened again, but there is quite a long period where each :open call immediately returns "Busy".