The app seem to be working fine to me on Firefox. Which feature not available on Firefox? I just did some basic editing in Firefox and all features I tried (haven't tried them all) seem working. Even motion tracking works.
The biggest problem is not supporting h264 encoding for the output.
Also as the preview playback is done with html video elements and those can't be started at a precise enough time, the timing of these videos are imprecise and may not align with other elements. This only happens at playback or scrubbing, not when staying on a single frame and the exported result should not be affected.
