This is a bug we have seen occur about once every 80 hours of lightroom use for the last few years. With every release of Lightroom classic we hope that it will be fixed only to be disappointed again.
What goes wrong is that when we work on ordering the photos in a collection that is filtered to only show images of 3 stars and above, occasionally the entire order is pretty much randomized while we rearrange items in that collection with drag and drop. It may have to do with creating virtual copies in between as the ordering step in our workflow is also the step when we create virtual copies of selected photos and turn them into B/W photos. We have not been able to create a clearly reproducible setup, but hopefully this is enough to debug this issue.
The problem occurs on multiple machines with different, often relatively new catalogues (we usually create one new catalogue per wedding we work on). We are usually on the very latest version of Lightroom classic with windows 10 pro and up to date drivers.
This problem regularly costs us an hour or so of work and is extremely frustrating when it happens. Please let me know if we can supply any additional information to resolve this issue. Thanks!