If there is a test in progress, you cannot minimize the window that is running the local test. Minimizing the browser window has some limitations from the Chrome browser, which puts the minimized tab into standby mode. In this case, the JS code is not executed, so the test stops automatically. If you want to run tests without disrupting your work, you can run tests in the cloud.
BugBug does not support multiple windows for recording and running tests. You are able to record tests with multiple tabs, but if your app use for example window.open() or 3rd party popups BugBug will not handle them. We have that on our roadmap.
If you use the LastPass extension during recording, you may have some problems with element selectors. As we know, LastPass changes the DOM of your page, so also selectors can be different. This can cause a failed test if you run it in cloud mode or another person will perform a local test on a different browser. Please disable the LastPass extension for incognito mode before recording or editing a test.