I was on 108 Hastings course at Thorney Island and Copilot solo was a 'must see' event as described in previous posts. On one of the solos the aircraft started to swing from side to side which resulted in one leg of the undercarriage collapsing. Luckily no one was hurt.
On the C130 OCU where I was instructing in 1967 the practice had ceased and there were no copilot solos, thank goodness! However it was more frightening having an outboard engine feathered by the staff captain at V2. It took some time for the lesson to be learnt that more aircrew have been killed practising engine failures than the unlikely event of the real thing. It has to be said that the original flight simulator at Thorney was quite basic and, I think, did not allow EFATO to be practised.