Devices are created by grouping multiple standard CAD entities. There are times when entities that are part of the device are not properly removed. Using the standard CAD ERASE command will erase the entire device. Use the Erase Part of Device command instead to remove the entity that is no longer needed.
To erase part of a device, go to
Ribbon: DM Electrical->Devices-> 
Erase Part of Device
Pulldown Menu: DM Electrical->Modify Devices->Erase Part of Device
You will be prompted to specify the part of a device to be erased.
Select entity in group to erase:
The entity will be erased.