7.0.3 installation error

win 10 / 1903 / update to 7.0.3 fails, because the installation routine seems to need some 6.1.8 sources (the version still running here), that cant be found… (I reported the same behaviour with failing 7.0.1 update) .

As I cannot include a small screenshot jpg, here is what it is complaining about:

Window 1:
“Seafile 7.0.3 Setup…
Installing Seafile 7.0.3
Please wait while the Setup Wizzard installs Seafile 7.0.3.
Status: Removing applications.”
Window 2:
"Seafile 7.0.3
The feature you are trying to use is on a network resource that is unavailable.
Click OK to try again, or enter an alternate path to a folder containing the installation packager ‘seavile-6.1.8-en.msi’ in the box below.
Use source:
C:\Users<usernamer>.\AppData\Local\Temp\Update-09ada725-6009-47c0-a078-e7bede071323\ "