Multiplying equipment with armor stands

I discovered a bug. I had been playing Minecraft without any problems until the day before. I discovered it around 8:00 p.m. Japan time today. I was late in noticing it, so it may have occurred earlier. When a player took an item equipped on an armor stand, logged out of the world in that state, and logged back in, the same item that I had just taken from the armor stand was returned to the armor stand, and the exact same item that I was originally wearing was returned to the armor stand. In short, an unintentional multiplication bug occurred. Before I noticed this bug, I copied and deleted the world several times as a backup. I wonder if this action is the cause. I don't like glitches that use bugs, and I hate this phenomenon where items that I have worked hard to obtain easily multiply. I hope to find the cause of the problem and solve it.