There are two files in c:\windows\system32.
riched20.dll
riched32.dll
You may have a different version on your old disk compared to latest Win10.
I've never had a problem like this since AssetX was born, but there have been numerous iterations of Windows since, and hence these two dll files have multiple versions.
However, I've not copied AssetX from Shane's website since PEV did some minor changes after he was given permission from Andi Smith's estate to act as guardian.
I have always copy/pasted the complete AssetX from my previous instal to the new one and ensuring it works with Trainz.
Currently that is the latest iteration of WIN 10 along with Trainz TRS22 core as well as AssetX, PEVTOOLS,TARDIS and Netpad++ on c:\drive (2TB NVME) of a new AMD MiniPC, coupled via a USB Type C gen2 to an external 10 TB hard drive containing TrainUserdata.
These RichEdit dlls would have been used I think to set up things like fonts etc as per the AssetX\Option\Preferences.
Considering what these dll files do you might like to check AssetX.INI [Position] :
[Position]
Restore=1
Top=6
Left=47
Width=1241
Height=740
AssetWidth=297
AssetHeight=250
OutlineHeight=241
MaxMode=0
When I had multiple monitors I had AssetX on a second monitor. Using the same setup on a single monitor, AssetX was off-screen.
Ian