I believe OTUs were often considered pretty hazardous places. Even the instructors were known to refer to inexperienced trainees as 'huns', in as much that they might be considered to be as dangerous to themselves as the enemy.It might be argued that, many squadrons continued ops with the transfer in of pilots already trained or conversion completed, while the others gingerly re-found their feet. Or, more simply, there's a war on, and you got on with it. Of course, what we don't have is the numbers of those who failed to qualify, and lost their lives under the heading of air accident, and there were a LOT of air accidents during WW2.
It would be interesting (and probably sobering) to see what the accident rates were.