alt_disk_mksysb on aix

I was able to reproduce your problem in the lab system.
- The problem occurs with EtherChannel configuration.
- The problem doesn't occur with non-EtherChannel configuration.
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To cut a long story short, it is a design limitation. The alt_disk_mksysb operation is not designed to be used for migration completely.
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The details are as the following. When the alt_disk_mksysb operation is performed, it is designed to remove old customized ODM and reconfigure devices from the scratch at first boot time in the target alternate disk.
Network configuration exists in customized ODM of the mksysb file. With the alt_disk_mksysb operation, the network configuration will be removed in the target alternate disk.
The alt_disk_mksysb operation extracts old network configuration from the mksysb file and keeps them in a script file in the target alternate disk and execute the script at first boot time from the alternate disk to make the new configuration as close as possible to the old one.
In that way, other Ethernet adapters can be configured at boot time before running the script, so that the network configuration can be restored at first boot time from the target alternate disk.
However regarding the EtherChannel adapter, it can't be configured at boot time before running the script. So the script will fail to configure network configuration since there is no configured EtherChannel adapter.
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So that is a design limitation with the alt_disk_mksysb operation. You cannot use your procedure for migration with EtherChannel configuration.
Since it is a design limitation, not a defect, we are not able to ask AIX development to change this through PMR process.
If you want EtherChannel configuration is supported under your migration procedure, you can raise a RFE(Request for enhancements) through the following link instead.