Pressing Stop is equivalent to closing and restarting Zorro, but not equivalent to SET_RESTART. SET_RESTART releases the TWS API, while Stop only resets the connection on the Zorro side. Both does not 100% guarantee to reconnect, since the TWS or Gateway can stay blocked despite their API reset. For reconnecting with 100% certainty they must be externally closed and restarted. From our experience, external restart is necessary with the Gateway, but not with the TWS. However this can of course change with any new version.