Problems with scrpage2 and tabu at new windows 10 installation

before I can describe the problem I want to give a short outline:

I work remotely for a small company. I am in direct contact to the workers which work at the head office, but I have no access to the computers there. But because only new employees are working there, I was choosen to care for the current problem. So I am not able to reproduce the problem for myself and just try to give a solution how they get their systems to work.

Basically they upgraded all their computers from windows 7 pro to windows 10 pro. Afterwards they installed miktex und upgraded all packages. Now occured the first problem: Although it was running on the old Windows 7-environment, the files led to errors in the new environment. Apparently something with the scrpage2-package.
For this problem they found the solution to include
RequirePackage{scrlfile}ReplacePackage{scrpage2}{scrlayer-scrpage} into the files.

Now there is a new error, that says that there is a missing { at the begin{tabu} (and we have a lot of tabus -> lots of errors).

I am really not understanding why the exchange of one package leads to an error in another one.

Maybe someone has some possible solutions to try, even without the possibility to reproduce the error.