[Required String parameter 'lang' is not present] with root cause

Am investigating

which seems to have happened in the background when i loaded GET /appointmentschedulingui/manageAppointments.page?*

That page loads well in a downloaded reference application 2.7.0 but somehow on some instances the same appointments scheduling ui module fails such as here with a 400 error. Reloading the same url doesn’t seem to log anything anymore, I added a default lang and am convinced the issue is beyond [Required String parameter 'lang' is not present] with root cause

BTW, has any one had issues loading manage appointments page?

so, after trying to access with out overwriting breadcrumbs, it works. Seems this happens in breadcrumbOverride

but appending &breadcrumbOverride=[{"icon":"icon-home","link":"/openmrs/index.htm","label":null},{"icon":null,"link":"/openmrs/appointmentschedulingui/home.page","label":"Appointment%20Scheduling"},{"icon":null,"link":"/openmrs/coreapps/findpatient/findPatient.page?app=appointmentschedulingui.schedulingAppointmentApp","label":"Manage%20Appointments"}] to GET /appointmentschedulingui/manageAppointments.page?patientId=* fails.