The troubles start once the /system partition is full right? It mean no more space for new apps (flagged as sys apps) user may install. Or that's something else i'm missing?
So enlarging the system partition is the solution.
Ps i copied app in /system and permissions fixed seems to work (i had 7.5 mb of free space)
Yes its because of system partition which is limited to 210MB if I recall correctly. Oversized rom is risky because user after flashing oversized system folder will get bootloop.
But if you have 7.5 MB free before Transfer I might bring it back. But we are not sure if we can support mione...
In the mi ione section there are afaik 2 scripts to resize /system partition (removing the "dualboot" feature i guess).
In the worst scenario it's possible to make a flashable zip of mi transfer (a single app lol) to people who still have free space or like to live dangerously.
If you need any df or stuff like that let me know.