I noticed that in current T4 version any submenus of offcanvas menu in mobile view can be open up for next level (when press on triangle icon), but never collapse back in original state after press on triangle icon again
look at any new templates demo, like JA Atoms ( https://ja-atoms.demo.joomlart.com/ ) or T4 blank demo.
but it works for example in old template demo JA Stark (https://ja-stark.demo.joomlart.com/). Seems it use old T4 version
I hope you can find this bug and correct it.