When I telnet to the Digi PortServer (II or TS), it power cycles the unit. 

Cause:

Although you maybe able to successfully ping the Digi PortServer (II or TS) and it boots up with no errors, you maybe experiencing a power
issue with that particular unit if you telnet to the Digi PortServer (II or TS) and it reboots.

Solution:

Contact Technical Support to determine if arrangements should be made for an RMA under the product warranty.