I had that issue as well. I think it's either Unlimited Supply or Ammo that does that. Not sure.
What happened in my case was, having infinite amounts of the collectibles made the quest complete next time i talked to the giver even tho i only had collected 2. After that, They were removed from my inventory and i was able to pick them up again but for no reason cuz the quest was already completed. Once i found out about it, i used the same thing to complete the baseball cards collectible quest.
Based on what i've seen and did, this only works for collectibles that accumulate in numbers. For instance, it doesn't work for the Vietnam Lighters or the Comic Books as each one is a separate item.
Did you actually activate the trainer pressing F1 in the game's main menu? Did you check your Numpad if it's enabled or if it still works?
Did you read this thread -> Link and followed the steps provided?
Yup, I even hear the "activated" after pressing F1 and after pressing any of the numbed keys to activate a cheat, but no effect in the game. Also tried verifying just now still same result. Strange...
Just added the exclusion as well and tried again... still the same issue. I feel like it must be the anticheat interfering