I don't have Transmit so can't check on this, but you may want to check out any log file that gets created. There may be something in a place like username/Library/Application Support/Transmit/logs, or you can open the Console program (Applications/Utilities/Console) and see what's getting written there. On the left side of Console there should be a list of logs, if not there's a Hide Log List button at the left of the toolbar. Scroll down it until you see something for Transmit. That's my best idea.