@JoPoV if the above post gets too complicated too quickly then the following might walk through the issues in a better organised manner (but it is still a long post) What is the best way to move a folder of photos with their respective *.DOP and *.XMP files? - #15 by BHAYT.
It might also be of interest to @ups and contains pointers to other posts where I try to explain the issues of moving data between systems. In these and the cache posts below the issue of retaining and moving the xmp sidecar file with the DOP and photo is missing because we had not become fully aware of the significance of writing and preserving the meta data when those posts were written.
Please remember that all that has been written has only been determined by testing and re-testing and not by any code inspection and with limited information from DxO.
Yet another set of posts that relate to moving data are here Cache file - #20 by BHAYT, Cache file - #22 by BHAYT, Cache file - #23 by John-M and Cache file - #29 by BHAYT.
Typically all the posts are long which stems from my I.T. days where I learned to explain the problem and the underlying reason that the customer was suffering that problem, then describe the potential outcomes of encountering the problem, then describe any ways of avoiding the problem preferably ones that had been tested and then “promise” a date by which it will all be fixed. This is not my product so I cannot make any such promises and arguably we are looking for additional features that make certain tasks easier and the risks of encountering problems much less!
At least I was earning a salary for that work and the customers were paying millions for their kit and for its support (hardware and software).