[deleted] error handling is currently quite bad in Bazaar. What happens is that any request that takes a bit longer is causing a timeout on the ajax call. I've currently catched this to refresh the page, because in most situations (during my tests on desktop) the installation succeeded. I now understand we have to do a bit more magic to make this work, I'm not sure yet how because Flarum does not yet support background queues.
I'll keep you posted, feel free to follow the issue on Github. Also we might have something in store for you that helps you manage your 9 installs ?