This I think has been caused by MDL-36878.

We have a 2 semester format (that renders by skipping alternate sections) starting at topic 1.

This is calling {[course_section_add_cm_control($course, $realsectionnum, $realsectionnum)}} function to render the tools to add new items (it also disables Javascript for other reason).

This in turn calls get_module_metadata().but since we've already called it for topic 0, the static variable $modlist has already been filled with the module information, which means the $sr value of the doesn't get up dated.

This means the drop down lists are always created with an sr=0 parameter.

This primarily affects multi-page course formats I guess...