We encountered an issue yesterday where a system update caused certain PhantomJS tests to start hanging and timing out. In response, the system rolled some of these tests over to Chrome or Firefox browser settings. The logic is part of an ongoing migration away from PhantomJS (which is quite old at this point and often begins failing as website modernize). In rare case, the rollover may introduce different issues into the test. We apologize for the inconvenience there.
If you've been affected and wish to move tests back to PhantomJS, please contact support. However, we strongly suggest either sticking with Chrome or using "Firefox (Legacy)" if you depend on specific legacy features like ":contains()" or network filters. PhantomJS will eventually be phased out so and this change will be required at some point in the future. However, we'll be making official announcements about that and providing a specific timeline so you can still run tests with PhantomJS, if it's your preferred choice.