by Ken Task.
Before rolling back mind trying something simple?
In config.php of site add a line that 'controls' the behavior of add act/resource (new/old):
// act chooser 0=old 1=new
// $CFG->modchooserdefault='0';
No need to restart/reboot ... takes affect upon next click of anything or refresh.
That worked with 3.9.x ... still works with 3.10.x.
'SoS', Ken