Hello everyone,
Today after a routine flight I closed the drone in the rest position and downloaded the photos and videos, I wasn't satisfied so I prepared the drone to perform a new flight, but something strange happened.

The left rear arm wouldn't open, it was blocked and in the end, with a little patience I managed it.

A small piece of plastic has fallen from the arm and the joint appears to be aesthetic damaged, as you can see from the photos.

I tried a new flight and everything seems to be fine, but I have some questions:

• where did that little piece of plastic come from?
• the drone is under warranty (purchased in July 2023) and I have the DJI Refresh Care lasting two years, should I activate the warranty or the DJI Refresh Care?
  

Hello, there. Sorry for the inconvenience. We will consult your issue with our engineers. About the DJI Care Refresh, did you buy it with the aircraft from our DI Store?

Hello, there. This piece does not look like the parts.
Please check whether the arms are loose, compared to the arms on the other side.
If it is loose and can not work properly, please send it back for diagnosis and repair.

To me that looks like it has broken off something that is perpendicular to the plane of the photo but I wouldn't guarantee that that is correct.
Where was the drone between the previous flight and this preparation?
If in a bag is there anything in the bag with an evident break and what way was the drone orientated in the bag etc.?

I can only guess that part of something got stuck in the arm joint and broke off. That jammed the joint and the force to move it made the damage.

If the arm is moving freely and still has that "detent" feeling (held in position when opened) I would explore the possibility of something other than a part of the drone getting wedged in there. Maybe get a close look at the vent areas and see if there is any evidence of something from one of those areas breaking off and working into the arm pivot area.

Does not look like an internal part. Kind of looks like a tip of some sort of antenna with it being tapered

This strongly looks like a piece of YKK brand zipper.

Only something hard like metal or a rock would damage the plastic like that. Also as the photo shows it must have been a sharp item.
I think the black plastic thing has nothing to do with it.