Hello, I found something interesting about that. I experienced the error, too, but before digging in my webspace, I checked my backend through Calypso app. I found it very convenient to manage my self hosted sites that way in the past and I was just curious how Calypso might behave with a defect Jetpack plugin. Quite unexpected, even while getting the error via browser, I was able to access my backend via Calypso app. At the time I have noticed the issue, the update for Jetpack was already available and I could trigger the update with Calypso.