Three doors under one arch is not three copies of the same door. Only the middle one is symmetrical.
The arched head runs continuously across the whole opening. Where the centre door sits, the arch is at its crown, and both halves of that door's head match. But the two outer doors each take a segment of the arch as it descends - and a descending segment is steeper on its outer edge than on its inner one. Their heads are handed: the left door's head is the mirror of the right door's, and neither will fit the other opening.
It is an easy thing to get wrong on the bench, where three door frames of similar size are standing together. So each is marked on its back for position the moment its head is cut, and it never moves out of sequence again. The hinges, the glazing rebate and the stop are all worked to that specific opening.
The test is simple. Close all three and look along the arch: the line should travel across the doors without a step at either meeting stile.