I had a mis-behaving checkbox input field on Firefox. The checkbox was working fine on Chrome and Safari - likely IE as well. But it wouldn't stay checked on Firefox - kept resetting itself to unchecked. For the short version, @jsobell on Aurelia's Gitter channel told me that Firefox triggers input attributes based on alphabetical order. I had a model.bind(), checked.bind(), and change.trigger() on the checkbox in question in that order. The change.trigger() was running last with the other browsers and first in Firefox.
It was sloppy code on my part, I should have processed everything in the change.trigger function instead of a kludge of model.bind and checked.bind with a change.trigger that was really carrying the main functionality.