when you try to drag and drop things from your inventory they don't get dropped, a few people have had this issue if not everybody. you can still drop things with q or drop stacks from inv with ctrl+q but you cannot just drop things by clicking and dropping out of the inventory screen. -Much love Xia
Hi!! Not an official response but just a personal note - for me this only happens when I have /auto enabled, as this command is used to put items directly into your inventory that are dropped near you, like when you break crops or a block ^^ This could potentially be the cause of not being able to drop items from your inventory.