Comment # 3 on bug 1093071 from Ladislav Slez�k

The package installed from the package manager work correctly because it
prepares the progress window for that. The other modules request installing a
needed package, but do not prepare a progress window. In that case the progress
cannot be displayed in the current window as it would be destroyed and it could
contain unexpected content after returning the control back to the module.

I think the fix could be opening a new window in the Package.Install and
related calls and closing it in the end.