It seems it's a bit of a myth right now that only modded servers have inventory problems. That's not true, we have problems all the time with our crates. Sometimes items will glitch out completely, sometimes you just cant rotate them or move them in a different crate or to your inventory. This occurs no matter in what container the item is, or in what part of the players equipment.
We usually solve it by either dragging it on the other side of the inventory first if it's on the ground, by taking the crates in our hands, or taking items in our hands first. One if these fixes it usually. However, sometimes none of the solutions mentioned above will work, often if the glitched out item is in a tent. It is, in my opinion, gamebreaking as it will deter new players and therefore damage the playerbase and the growth of the game. It will even annoy vets to the point of quitting since it just takes so much time to deal with.
This is happening on most official servers in my experience. It will usually work fine for ca. 10- 30 min after a restart but after that most items and containers in bases with a lot of loot will start to glitch out.
This needs to be fixed, it's especially annoying if you have a base and you have to plan in serious time and effort just to sort out the inventory because it takes that much time right now.