Sorry to jump on your thread MR.Oscar.Edward but I have a similar issue.
When I launch projects made in 8.5.3 on 32 bit I keep getting a missing plugin for Ampltitube 3. I remap to the new file path for 64 bit plug ins and Amplitube is found straight away. I save an X1 project but on relaunch it just comes back and for every projectc created on my onld 32 bit system.
It's not life threatening as it only takes 2 seconds to remap, just a bit annoying, I thought saving would remember the new file path for Amplitube .dll file.
Thanks
Dean