This issue is intermittent but occurs more frequently when a user adds, updates, and removes multiple service stops from a client record without saving between each change.
To avoid this, save the client record between each service stop change. For example, if a new service stop is being added and one is being deleted, save after adding the new service stop and save again when the old service stop is deleted.
If you have accidentally added an open-ended service stop to a client record that needs to be deleted, add an end date to the service stop before deleting it. Deleting open-ended service stops without ending them first is a known cause of this issue.