Ultra-fast charging is still in the early phase of development - here is one of the issues reported at the IONITY network.
According to Bjørn Nyland, the charging can randomly stop. It happened already multiple times at various states-of-charge and power levels, so the cause is not yet known.
It might be related to the Model 3 (software) or the Tritium chargers. One guess is also that the specific metallic sound when the charging is interrupted is caused by quick temperature changes when charging a not heated battery pack at high power.
IONITY is aware of the Tesla Model 3 problem and reportedly is trying to help by re-starting the sessions at no cost.
More tests would be needed also at other high-power chargers to see whether it's the Model 3 or Tritium only. For now, reports from other (non-Tesla) electric car owners suggest that maybe it's more a Tritium issue.