First off all I don´t have those models but four years ago I had a similar problem with other devices.
My issue was that the customer had the same license on several terminals. Add manually the license has the possibility a human error.
When the emulator start scan the LAN and detect if this license are being used for another device. If it´s detected the emulator removed the license from device ,
Before this action in device's screen showed an informational message with the text of license duplicated .
My solution was install a Wtelnet license server (freeware) to manage those licenses.
When the issue appears the devices automatically contact with the license server and they acquire the licenses automatically. For the customer is transparent.
Try it it´s very easy to install and configure and you wont have more headaches.
I hope It helps you
Many thanks for you message, much appreciated.
We have had a situation where the same license was added onto more than one device previously and we believed we had rectified that problem. The issue we have is that these devices are on a managed service contract so they are swapped out as and when a unit goes faulty. A replacement device is sent to the site with the identical TE license information and the damaged unit is taken off site. Both devices are not powered on during this time.
The users are not reporting seeing any pop up messages about duplicate licenses on the devices. They only report that the units are booted up and when Telnet starts up, when they press enter they are presented with the pop up asking for a new license.
It is only a small number of units but I am just wondering if there are any other possibilities other than duplicate licensed devices that could potentially cause this to happen.
You should contact the re-seller or company maintaining your licenses and explain the issue to them.