Assembly Constraint is not associated to a part occurrence.
High, Medium, Low.
Assembly Constraint (relationship) object is not related to an equipment item anymore.
The cause is currently unknown.
Some commands may not work properly.
Possible erroneous or inaccurate Equipment reports.
What You Should Do
If the problem is local to one or a few pieces of equipment:
Open the model.
Delete the equipment.
Save the session.
Refresh all session files with a workspace including the equipment.
If the problem is widespread on all equipment:
Restore your most recent backup using the Project Management task.
Refresh your session files.