This is exactly why people need to attribute properly, ideally even with sounds they paid for, so that people know that they came from an existing library and can look it up them selves if they are suspicious.
It would get rid of so much trouble... And it's not even hard. You just say all this group of sounds came from this library, this group came from here, ETC. No need to mark each track.
It really helps if you write it in a document while creating the sounds as well, plus you can just copy the folder names for speed. Then it's super easy to remember.
Example:
Inventory sounds
Adobe Audition SFX: Foley
PM Sound Effects: Tactical Backpack
Footsteps
The Sound Pack Tre: Footstep Loops 2
Soundopolis: Foley Plus
Red Libraries: Mini Game Pack 1
Weapons
PM Sound Effects: Abstract Guns
Freesound.org: filmmakersmanual
Fesliyan Studios: Weapons
Airborn Sound: Free Firearms
Adobe Audition SFX: Weapons
Motion Array: Free Gun Sound Effect
Sound of Italy: Explosions
Airborn Sound: Medieval Weapons
Freesound.org: bay_area_bob
Soundopolis: Swoosh Whoosh Swing
Bad Studios: Gore Source
Red Libraries: Body Fall Freebies
Vocals
itch.io: Dogl's Sound Pack
itch.io: Super Dialogue Audio Pack v1
opengameart.org: RPG Voice Starter Pack
Articulated Sound: Starter Pack
UI
Currently Untitled Audio: Soundflakes-06-2020
Digtal Rain Lab: Bleeping Buttons
Ambience
Thomas Rex Beverly: AMB10_Northern_Rockies_Common_Loons
Skyes Audio: Dormant Village
Articulated Sound: Starter Pack
Soundopolis: Natures Fury Wind 01
Hzandbits: Urban Winds II
West Wolf: Nature Sounds
Music
Incompetech.com
Sound Ex Machina: Endless Drones Light
Smart Sound FX: Dark Textures
MatiasMacSD: INDICT FREE