I'm having the same issue - items disappearing from inventory.
Windows 10, playing in English. I don't have Jungle Adventures. I have never used CC or mods. I haven't used any cheats in *this* save, though I have used it in different saves (because I also had the issue where saving a game overwrote a different game, I keep separate save folders for each of my sims/families/games).
My Sim was going around collecting stuff. One day everything in his inventory disappeared except for the snow globes he'd bought at the flea market. I repaired the game, but the issue was still there. Before this issue, I've previously repaired, reset, and completely reinstalled the game trying to fix other bugs (I had the issue where the rocks weren't respawning - either reinstalling or some patch must have fixed that, cause now they're respawning again). I think this may have started with the last patch - at least I didn't have the issue before then.
I restored the save to a previous save to get all that inventory stuff back (losing, of course, stuff he'd collected since, as well as his roommate's promotion). I kept a closer eye on the inventory, and sure enough, some items were disappearing randomly. He'd collect stuff, come home, and the stuff he'd just collected wasn't there. Also, the elements he'd gotten from the geo council were gone. The Collections (when you click on the icon in inventory) had them in there, but he no longer owned them. The missing items are not in the household inventory or the other Sim's inventory or anything like that.
I don't know if related but the snow globes collection was all purchased in the flea market - I mean, my sim never bought a snow globe himself, just bought the whole collection all in one shot at one visit to the flea market - I don't know if that's how it's supposed to work. Usually at the flea market I can buy a couple collectibles but not the whole collection. Also, my Sim's roommate is a painter, and she's having the issue where if she leaves the lot, she can't Resume the painting - I have to put it in her inventory then put it back on the easel for her to be able to continue working on it.