Wacs stop with error message during SendAll/SendChg
From Zenitel Wiki
Sometimes it can happen that Wacs will stop during Sending of Directory numbers with an error message stating that "Serial Communication is dead, Retries exhausted". This can happen both in SendAll and SendChg operations. This normally is caused by faulty records in the Directory number table. To find these faulty records, open the Directory&Features window and sort on Directory numbers (click on the Dir No header in the list). Now all features that are dialed during connection is listed first in the list (symbolized with a * to the left of the directory number). In this situation you will find one or more Feature 9 directory numbers among those numbers)