We’ve all been through a lot with this game, even those of us who actually enjoy the high pace FPS style of this game, as some would really like the place to be slow and match times extended.
I’ll offer some advice. Take what people say hear with a heaping shovel of salt and, as far as your original issue, it might have been a recent glitch that causes you to lock into ADS, your character might have partially clipped through the surface of the ground, or it could have been a de-syncing lag type of issue.
Long story short, maybe just upload a recording to YouTube and post a bug report in the Bug section and, unfortunately, accept that these things are just part of the game and not every match will be fair.
EDIT:
Well there ya go. Glad you at least know what happened.