That there have been substantial breaches of the operator's obligations in the agreement or persistent delays in making payments under the agreement. (lawyer-monthly.com)
The obvious difficulty with the doctrine of fundamental breach is determining how substantial a breach must be before it is considered «fundamental». (tdslaw.com)
However, if it a case of continual non-payment of rent, payment will not void the eviction notice for substantial breach. (slsedmonton.com)