Hours upon hours spent grouping design assets into stacks both inside of regular folders and within collections, then after a restart, most of these stacks have disappeared. Happens randomly to random stacks, and it's driving me crazy! I cannot keep an organized design asset library due to this bug. I am on Adobe Bridge v18.104.22.1688
I experience the same behavior. When dragging items into a subfolder, all the stacks in the parent folder disappear. However, if you go out of the folder and back in, the stacks are back.
Do you observe this behavior when you are doing some particular operation. All your files on your local disk or on network or mix of it.