In your opinion, what was the classification of this incident according to the ERC matrix ?
In my opinion, it lies between 2 and 21.
The flight path was never really dangerous. One call from one pilot was enough to resolve the issue.
There are other systems that help prevent escalation into more serious trouble (EGPWS, TCAS,..)
I have the same question, regarding crashes this time. Ask the exact same questions, however take the accident scenario for question 1, and what should have happened for question 2.
Then go into the matrix. For example AF447 should have been a 502, at worst. Concorde crash was a 2500.
However, some deadly crashes should have been classified 50 or 102. There are many examples where lots of barriers synchronised to be all defective together, whereas they shouldn't have been.