Should be resolved now.
The actual importing of the old forum data was the easy part (built into Xenforo). Going through all the settings, that's an ongoing thing - there are literally hundreds of settings. Most imported fine, but not all. I spent a lot of time on a test server, but live users have a way of finding all kinds of things one man can't.
Titles that start or end with numbers are wrecking havoc on Xenforo's built-in VBulletin redirect system, and TDR is loaded with them! XF expects thread/forum numbers after the title. VBulletin expected them before. So when it sees a thread with a number before AND after the title, it doesn't know if it's an VBulletin URL to redirect, or if it's a new format Xenforo URL! When it gets it wrong you have page not found errors, hovering that doesn't pull up previews, etc.
turbodieselregister.com/5.9L-Engine-Problems.23840/ is an example of a URL which confused it.
I'm having to write custom redirect code for each type of format as they happen while trying to not break previous code while I'm at it. I *should* have the vast bulk of it working now.
Add on top of that the articles section, which Xenforo doesn't import at all, having to write a custom importer, 15+ years of legacy custom code written to support magazine and magazine subscribers... and my days are full!