Setup from very old Makeself cannot extract anymore

[commel]

I am trying to extract an old packaged software on a modern linux system (openSUSE Tumbleweed).

./monochrom-SUZ2--version1dot2.sh 
Verifying archive integrity...Error in check sums 2167415832 != 2079859116

You need to download the installer again, as it is corrupt.

If your download appeared to be successful, try a different
browser. Some browsers, such as Netscape, are known to corrupt
some types of binary files by trying treating them as text.

As the installer was made with an old Makeself 1.5.5, I've tried the POSIX-Environment Variable already:

_POSIX2_VERSION=199209 ./monochrom-SUZ2--version1dot2.sh
Verifying archive integrity...Error in check sums 2167415832 != 2079859116

You need to download the installer again, as it is corrupt.

If your download appeared to be successful, try a different
browser. Some browsers, such as Netscape, are known to corrupt
some types of binary files by trying treating them as text.

I've already tried to extract the tar itself by removing the script until the binary starts, but that did not work either, as tar thinks the tarball is broken.

Has anyone a hint for me, what to try next?