I remember there were some changes from 2.x to 3.x that may have to be made in order for the upgrader to work?
You may have to upgrade from 2.x to 3.x first?
or else, we have to re-build this page
Though I think we are going to have to tell the client "No more tooltips"
So this seems to have sorted the issue: https://stackoverflow.com/a/15585700/4161644
Does Silverstripe have any issues with using Barracuda format and compression?
they have a form with a load of tooltips (that contain HTMLText)