Desperately I tried also adding fsync, to no avail, both issues remain.
Non-working patch attached.

Maybe dynamic-wind is an inappropriate pattern here?

If I interrupt installation using Ctrl-C (which I normally don’t,
instead I unplug Ethernet), then I have to press Ctrl-C twice.  Maybe
that could be related to why I need to resume twice?

I’m in the dark.

Regards,
Florian