What is the specific process are you using to transfer the systems?
I've experienced that to; not all the time and very rare. Process for me <> System Tree <> Actions <> Agent <> Transfer Systems <> Select New ePO. My guess, it may have something to do with the system performing the normal check'in during the time of the transfer....just a guess
After the system is marked for transfer it will remain in System Tree until it communicates with the ePO server. A flag is set in the database to identify the system is to be transfer to another ePO server. Once the system communicates to the original ePO it will then be informed it should transfer to the new ePO and after the successful ASCI the system should be removed from the System Tree.
If redeploying McAfee Agent the system will remain in the System Tree of the old ePO server.
So doens't seem like this is normal behavior.
Actually I migrated a dozen of agents this morning and they all disappeared from old ePO console.
I also tested to reactivate the agent after sending the instruction of migration but it still disappeared on old ePO.
My guess is indeed a task which tried to deploy the agent during the migration.
Thanks for help!