I recieved this error when I tried to open my saved game including add-ons:
(https://simutrans-germany.com/files/upload/fatalerrormaglev.PNG)
How to fix?
Yes, I have all the add-ons, this is in .pak128.
No you don't, or you did not start with addons.
It seemed that my computer had compressed these files and that I may forgot to press load with add-ons. But still, why are there Pak128 old and Pak128?
If a new pak is installed, the content of the old pak is kept under pakname.old. (Any pak with already this name is deleted.) This is especially useful for paks like pak128.german, where the next release tends to be incompatible to the previous one.