If i try to take a screenshot, for the next 5 or so minutes the screenshot sound effect will go off repeatedly and lag my game. When it's finally over, I'm left with over 50 screenshots of the same exact thing. Wtf is going on? This only happens on BF6 - no other games have this issue with Steam overlay at all.

Hey, there
Found some others around this with other games as well. Here is what I found that may help you out.
Fix 1: Disable the EA App Overlay (Primary Cause)
Even if you own and play the game through Steam, the EA App runs silently in the background and hooks its own overlay into the game, causing severe input locking and micro-stutters.
Open the EA App on your desktop.
Click your profile icon in the top-right corner and select Settings.
Go to the Application tab.
Scroll down to In-game overlay and toggle it OFF.
Fully restart Steam and launch the game.
Fix 2: Rebind or Change the Screenshot Key
F12 can conflict with function key layers or in-game bindings. Rebinding it clears stuck hotkey handles:
In Steam, go to Settings > In-Game.
Find Screenshot shortcut keys.
Change it from F12 to a key far away from standard game inputs, such as F8, Pause/Break, or Numpad Asterisk (*).
Fix 3: Turn Off "HDR Screenshots" / Steam Overlay Notifications
If you are playing with HDR enabled in Battlefield 6, Steam attempts to render two versions of a screenshot (SDR and tonemapped HDR). When the overlay hitches, this thread can loop endlessly:
Open Steam Settings > In-Game.
Turn OFF "Save an uncompressed copy" if it is checked.
Turn OFF "Display a notification" for screenshots (the notification pop-up itself often causes the overlay thread to crash and loop).

Had the same thing happen but in BF1. Maybe it's a steam issue.

I fixed it by disabling Steam's 'Game Recording' feature, which I was using to save clips. I turned it off because that too started getting glitchy lol, and now my Steam screenshots work fine in BF6. I use a different clipping software now.
So it may be a Steam issue after all, although I've still run Steam's 'Game Recording' feature in other games and taken screenshots without issue. But those other games might not have been as graphically demanding.