I have a problem with the new WPI 5.x.
I guess it's a known problem but can't find a solution anywhere.

In my config.js there are allot of 7z sfx installers(office2k3,.net framework,etc..)
After they are extracted they start installing on their own.
The problem is that this new WPI doesn't wait for them to install....
It proceeds with the next item therefore not installing everything properly.

Is there a fix or something for this?

I have a feeling I know what the problem is. WPI is doing what is supposed to. It is starting a process, the 7zip extractor, waiting for it to finish, then continuing on to the next step. A way to do this is to write AutoIt scripts to run the 7zip file then run the installer.

Yes that's what I think to.
However this isn't the behavior one would expect from a installer program.
The old WPI didn't do this and waited nicely for the process to complete.

Think I am going back to good old WPI 4.x

same thing happen to me. the 2nd installation starts before the first one finish its process. kinda stupid especially when using autoit sript installation.