JLC Master Calendar (ref. Q151842A, cal. 924) date-month change question

Hi all

Few days ago (March 29th) I bought a used JLC Master Calendar ref. Q151842A (40mm, not newest version, cal. 924 I guess) from 2013.
As it was set to correct day, date and month so I just adjusted moon phase when I came home.
Today it switched the date to 1st but month remained on March which I manually (by pressing the button at 2) corrected to April and I thought it is the way it's suppose to be.

But some crazy bug in me wanted me to try changing date (by pressing the button at 4) all the way around to 1st again.

And I noticed that it month changes but when I switch the date between 27th and 28th?

Is that correct? If yes that a simple question, why?

If not is there anything I can do (pushing some buttons, maybe two at same time or something) to correct it or set to switch month when I want or does it need to see a service/watchmaker?

Thank you in advance.

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Sounds like it needs to go to the factory for an adjustment....

By: watchme : April 2nd, 2015-11:15

The Master Moon and both Master Calendar models all adjust the month after 31 days, which means that there are 5 months when you will need to adjust the date forward via the corrector at 4 o'clock. The months are supposed to advance automatically as the d...

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