Encountered a Glitch I haven't Seen Before, Nor Have I Seen Anyone Talking About It Online.

I was looting around Airfield, when I found an M4 in a Barrack. I picked it up, and it had a magazine in it. The magazine had 16 bullets left in it, and the M4 had a round in the chamber. I took the magazine out of the M4 perfectly fine, but when I put it in my hand and attempted to combine it with some 5.56 in my inventory it didn't give me the "Hold RT to Load Magazine" option, still only the "Hold RT to Empty Magazine" option.

Has anyone else encountered this glitch?
If so, are there any ways to fix it?

Thank you in advance.

Sidenote: This is my first time filing one of these reports, my apologies if I've done anything incorrectly.