Symptoms
GetSubscrTerminateDate_API for the subscriptions without termination date returns result different from described in the documentation (in the API guide it is written that NULL is returned for active subscriptions).
Cause
In PBA < 5.5 the method returned the value -2147483648 (which is NULL). Since PBA 5.5 a message "Termination date is not specified for Subscription X" is returned. Documentation will be updated with one of the product updates (documentation bug #PBA-54697).