Phoenix wallet is a unique Lightning wallet in that, among other things, it allows the user to restore channels by simply entering their seed. According to ACINQ's blogpost, this is how they achieve it:
TL; DR: Each time channels are updated, Phoenix sends an encrypted version of their data to its peer. This allows for easy backup/restore of channels while maintaining privacy.
In the case of Phoenix wallet, the peer is always ACINQ, but my question applies to any similar peer backup solutions: what's to stop the peer from making me recover an old channel state, and claim all my funds when I try to close it?