Update Win Client 6.1.8->7.0.2 fails

It seems the 7.0.2 installation procedure needs the 6.1.8 installation package?

Executed seafile-7.0.2-en.msi
->Window A:
Seafile 7.0.2 Setup
Installing Seafile 7.0.2
Please wait while… bla bla bla
Status: removing applications
triggers -> Window B:
Seafile 7.0.2
Accessing the feature…
Click OK or try again, or enter an alternate path to
a folder containing the installation package 'seafile-6.8.1-en.msi"
in the box below.
Use source:
(In the box:)
triggers -> Window C:
Seafile 7.0.2
/!\ The Path C:\Users\ubenedix\AppData\Local\Temp\Update-09ada725-6009-47c0-a078-e7bede071323\seafile-6.1.7-en.msi
cannot be found. … bla bla bla …

The missing file seafile-6.1.8-en.msi and the folder containing it obviously was deleted eventually when cleaning up the disk.
It had been stored in a /temp/ directory… The 7.0.2 installation progam relies on a 6.1.8 msi file in a temp directory?

This is Win 10 prof. / 1809