So, I "JUST" realised why Jimin had safety pins during the no more dream era .-. I know right. Wow. I'm a terrible person, cause I just noticed it 

I noticed Jimin had safety pins on his shirt when I was trying to zoom in to see a Hoseok at the corner and accidentally I zoomed in on Jimin's shirt and saw many safety pins. I might have noticed those pins back in that era and forget about it .-. So here are some pictures. Zoom in to his shirt just above his abs to see safety pins. 

In the picture below if you look closely, you can see he chain on his his wrist also has a safety pin. The chain looks like it was broken. And if you look closely at the shirt, you can see safety pins clipping those chains to the shirt so that, they won't fly to his face during the performance (eg:during the flip) and also because the chain looks damaged. Which you guys probably would have already known. I'm the idiot.