Okay, In case there's a rare occurrence of someone else stumbling on this, I changed my way of accessing the XF user information by using the XF API and session info. All good now :)
Hiya
I'm using this for both Wordpress and Xenforo, and have no issues with it in the main.
However, I've a bit of code I'm using in Wordpress to get the current user from Xenforo, so that I can show various items depending on usergroups
Basically along this lines
$fileDir =...