Hi, sorry to break into this old topic,
But I have the same problem and it appears only to happen when I use Raidrive to connect to my webDAV drive.
If I use the standard Windows 10 webDAV client and have my cloud as a network drive, this does not happen. Also if I use an other program, AirliveDrive for example, this does also not happen and the orginal date is kept.
So, only when I acces my cloud drive, Trans IP (Stack), by using Raidrive and copy a file, the date is adjusted to the current date/time. Which makes me think that this is somehow caused by Raidrive. For the rest I`m perfectly happy with Raidrive, but would like this issue to be resolved.