Orient Multi Month Calendar Power Reserve
Cal. EX01

I noticed that the watch stopped consistently at 40 seconds - even the Power Reserve showed 40 hours

So I opened the back and removed the auto winding system to see whether there was any dirt on the second wheel that would have causted the stoppage. Interestingly, as soon as the auto winding system was off, the watch happily ticked without showing any sign of slowing around 40 seconds.
I have marked the positions of the wheel that is held by the magic lever with yellow circles. As of now I do not really know what happens the watch to slow down around 40 seconds, but I can tell that it is definitely some interaction with the auto winding system. A fellow forumner Zeb aka Dan had also observed the same effect on his Orient Beast. I have also observed that the position of the rotor definitely affects the stoppage. Thus I trust it has to do with the auto winding system. I will keep investigating for sure. The removing and reassembly of the magic lever and the oiling of the jewels of the magic lever wheel has definitely reduced the effect but I do not think that was the sole reason for this behavior.