The magnetic phone mount kept the metal plate and let the phone leave alone

I attached my phone to a magnetic dashboard mount while the car was parked.

The phone held normally.

When I removed it, the thin metal plate inside the phone case stayed attached to the mount. The phone came away without the piece that made the system magnetic.

On the next attempt, the case touched the mount and slid down immediately.

I returned the car to park, removed the case and found that the plate had shifted because it was loose rather than secured in the position recommended by the mount instructions.

I did not drive while experimenting. I removed the plate from the mount, cleaned and reassembled the system according to the product guidance and tested the hold while stationary. The phone stayed attached through gentle adjustment.

The magnet had worked perfectly. It held the correct component more strongly than that component was connected to the phone case.

What is the safe setup? Use compatible mounting parts, secure the plate exactly as directed, test while parked and keep the phone outside the driver’s sightline and control area?