In CORE, look at the entries for What Were Once Men in the Doomvault mission and Corroders in the Monster section for inspiration.
For Corroders, generally I telegraph the acid all over the cavern, and then it’s simply: if you take damage, make a random roll and lose that piece instantly. For example, if you have loot in 8 slots on your sheet, roll a d8 and lose the item in that slot. Or you can run them like in the book with a threshhold: if you take over 5 damage in a single hit, lose random gear.
I have also made players roll for random gear loss after a fall from a dizzying height, whenever they end up unexpectedly in water, or whenever they end up in muck or quicksand. Items have a tendency to get lost in those scenarios.
There is also a chance if characters get captured (say, on a wipe) that they might lose all of their gear or they might not get it all back if they recover their stash (the monsters took one or two items).
Characters can lose items on a blunder, and they can have items break or be lost if the items have a tag like brittle or volatile, or have items be broken if they use the items in a way the item wasn’t designed. In my recent campaign, one of my players used THE Sword, the most powerful artifact in the game, as a pry bar. That didn’t end well, but it did prompt a fun quest to reforge the sword.
Finally, having monsters that steal loot like pilfering raccoons (think rat thieves in Borderlands) is a fun scenario. Every time the monsters make contact, lose a random piece of loot. If players can kill the mob before it leaves the board, they can get the loot back. With enough of these things zig-zagging across the board, that is a fun encounter in and of itself.