It's not unusual. The hour recorder is driven directly from the mainspring barrel with a friction spring and pinion arrangement, so it's driven from a different part of the watch than the seconds and minutes recorders are (those are driven off the 4th wheel). Some are closer than others, and it can be affected by how well the hand is set on as well, but even with the hand set on perfect, they can still be out slightly.
The hour recorder is the least precise counter certainly, and really if it tells you that you are in either the first or second half of the hour, then it's doing it's job.
Cheers, Al
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