Description
Due to a problem in the Quartus® Prime Pro Edition Software version 19.1, the automatic register duplication by hierarchical proximity (DUPLICATE_HIERARCHY_DEPTH) may be ignored when applied with an 'altera_attribute' synthesis attribute.
Resolution
To work around this problem, set the DUPLICATE_HIERARCHY_DEPTH assignment in your Quartus® Prime settings file (.qsf).
set_instance_assignment -name DUPLICATE_HIERARCHY_DEPTH -to <register_name> <num_levels>
This problem is fixed beginning with the Quartus® Prime Pro Edition software version 19.4.