There is no solution, this is a bug. You need to downgrade your version of AE.
Thanks for your answer. Good to read that I am not totally stupid. As am using CC, I am afraid I can't downgrade, so I have to be patient for the moment Adobe will fix the bug. I have found a 'workaround' by 'copy/pasting' the "path" from an earlier AE file. Not the most efficient work around but it works.
Thanks for sharing what worked. It reminded me of something, so I poked around a bit. Turns out you are not the first to find that workaround! Path animation bug in Text Presets of AE CC2015 (Win)
I would be unsurprised to find that particular bug to be among those fixed in the next update: What’s new and changed in the upcoming update to After Effects CC 2015