At first glance, that buffer looks like a chewed up penny.
I don't know but if I had to guess, it looks like the buffer retainer pin isn't held as deep as it should be. Like the buffer is slamming into the larger diameter portion of that pin.
Which seems like it would interfere with the boltcarrier travel as well.
This uneducated guess has been brought to you by Kroger's Medium Roast Coffee and Orowheat homemade cinnamon toast.
Jon