Related to MDL-64886, another issue we have found as part of the enrol_get_users_courses webservice is that get_course_progress_percentage can take a long time (as much as 13 seconds on our larger courses, between 0.5 and 1 seconds on our typical courses).  It doesn't take many of these to hit the 30s timeout from the app's webservice calls.

Fortunately, this appears to be an easy fix.  The call to $completion->get_data() in /completion/classes/progress.php has the wholecourse argument set to "false" even though its looping over every module on the course. Setting this to "true" appears to do the job.